Creating Permanent Masters for Mold Making

December 18th, 2014

This blog entry focuses on how to make hard rubber or plastic copies of original masters. There are a number of good reasons to create “permanent masters” of originals:

  • Some original masters (e.g., stone) can easily break or crumble.
  • Using original masters multiple times requires re-application of sealing agents, release agents and caulking.
  • If you produce molds in large volume, multiple identical masters allow for production of multiple molds simultaneously.


How to Make Copies of an Original Master

In this example, we’ll focus on a veneer stone master, which is composed of multiple side-by-side stones affixed to a baseboard. This master is designed to create a multi-cavity mold.

Veneer Stone Master

To create a duplicate master of these veneer stones, we choose to use a hard polyurethane rubber: Poly 75-80 Liquid Rubber.

On the Shore Hardness Scale, Poly 75-80 falls on the A scale at 80. It is a hard material, but will not break if it falls from a shelf, for instance.

Shore Hardness Scale_Polytek

Polyurethane plastics in the Poly 15-Series are also very popular for this use.

Step 1: Prepare the Existing Mold

The mold pictured below is made from Poly 74-20 liquid rubber. It was poured over the veneer stone master pictured above and was made several years ago (for a tutorial on how to make a veneer stone mold, visit our YouTube Channel).


Place the mold on a baseboard. We use melamine-laminated particle board for this tutorial.

Poly 74-20 Rubber Mold

To prepare the mold, first start by cleaning it off so there is no dust or debris that comes out with the master copy. Denatured alcohol is a good cleaning solvent, but care should be taken due to its flammability. Apply denatured alcohol to a rag or towel and wipe the mold.

Clean the Rubber Mold

Seal the edges of the mold so that casting rubber does not run beneath it. Typically, we seal edges with warmed plasticine clay; however, this particular mold has been exposed to quite a bit of release agent over the years and the clay has difficulty sticking directly the rubber.

We apply hot glue to the edges and smooth it out with a tongue depressor.

Seal Edges of Rubber Mold

Then we apply warmed plasticine clay over the glue and smooth it out.




Step 2: Construct Mold Box

Construct a mold box to contain the casting material that will be poured into and over the existing mold.

Prior to constructing mold box walls, spray release agent onto the exposed baseboard and brush it out with a dry brush (it will be more difficult to reach once the walls are constructed). The casting material is a polyurethane rubber, so Pol-Ease® 2300 Release Agent is used.


Assemble mold box walls and secure them. We use melamine-laminated particle board for the walls and secure them together with C-Clamps.




In this case, the finished duplicate master will have built-in walls, so the mold box is lined up 1/2″ beyond the exterior walls of the existing mold. The great benefit of having built-in walls is that there is no need to create a containment area around the permanent master every time a mold is made.


To prevent the mold box walls from lifting or “floating” when the rubber is poured, we secure them to the baseboard with screws.


Seal the exterior edges of the mold box with clay so rubber does not seep out (hot glue or caulking also work).


Also seal the interior corners of the mold box.



Step 3: Apply Release Agent to the Existing Mold

Very thoroughly coat the existing polyurethane mold with Pol-Ease 2300 Release Agent. Liquid polyurethane rubber will adhere readily to cured polyurethane rubber, so it is imperative to thoroughly cover the mold.


Brush out the release agent with a dry brush to promote even coverage.



Step 4: Calculate Amount of Casting Material Needed

To calculate the amount of casting material needed to make the duplicate master, use the following calculation:

  1. Determine the volume of the mold box (L” x W” x H”). In this calculation, incorporate at least 1/2″ of space above the top of the existing mold.
  2. Subtract the volume of the existing mold from the volume of the mold box.
  3. Take the result of that calculation and divide by the specific volume of the casting material (the specific volume of Poly 75-80 is 26 in³/lb). This final result is the amount of rubber (lb) needed to complete the duplicate master.



Step 5: Measure, Mix & Pour Liquid Rubber

Poly 75-80 Liquid Rubber has a mix ratio of 2A:1B, a pour time of 45 minutes, and a demold time of 16 hours.


Measure out Part B on a digital scale (we pour Part B into the mixing container first because it is lower in viscosity and is less likely to cling to the sides of the mixing container).


Measure out Part A on the scale.


Thoroughly mix the rubber, scraping the sides and bottom of the mixing container several times. Mixing in a “figure 8″ pattern is also a good technique. We use a Poly Paddle to mix the rubber.

Thoroughly Mix Poly 75-80

When thoroughly mixed, pour the rubber into one corner of the mold box and allow it to rise.

Poured Rubber Over Mold

Pour rubber into rubber; avoid pouring directly onto the mold.

Pour Into One Corner

Pour Rubber into Rubber

The rubber should be at least 1/2″ over the top of the mold.

Permanent Master from Existing Mold

To help eliminate surface air bubbles, spray Pol-Ease 2300 Release Agent across the surface of the rubber immediately after pouring.

Pol-Ease 2300 Release Agent Aerosol Can

Allow the rubber to cure for 16 hours before demolding. Final cure properties are reached in about 7 days; however, molds can be used, with care, after curing for 24-48 hours.

16 Hour Demold Time


Step 6: Demold

Remove the screws from the baseboard and then remove the mold box walls; a putty knife can be helpful for wall removal.



Turn the mold over for easier removal if necessary.

Flip Mold Over for Easier Removal


Carefully loosen the edges of the mold from the new master before removing the entire thing.

Loosen Edges of Mold



Mold Making Tutorial

The finished permanent master with built-in containment walls:

Firm Rubber Permanent Veneer Stone Model

Poly 75-80 Liquid Rubber to Make Duplicate Model

Poly 75-80 Liquid Rubber - Polytek

Trim the edges if necessary.

Trim Edges of Master


Step 7: Making a New Mold

To make a new mold of this master, first select the appropriate mold rubber. We have selected Poly 74-20 liquid rubber (the same rubber as the original mold) for this tutorial.

Poly 74-20 is soft polyurethane rubber (Shore A20) with a 1A:2B mix ratio; it is very popular for veneer stone applications.

Apply a suitable release agent (i.e., Pol-Ease 2300 Release Agent) to the master and brush it out with a dry brush.

Apply Release Agent to Rubber Model

Measure, mix and then pour the Poly 74-20 rubber onto/into the new Poly 75-80 rubber master.

Pour Poly 74-20 Liquid Mold Rubber

Poly 74-20 Mold Rubber

Poly 74-20 Veneer Stone Mold

Low Viscosity Poly 74-20 Mold Rubber

Poly 74-20 Urethane Mold Rubber - Polytek

Demold after 16 hours.

Demold New Rubber Mold

New Master & Rubber Mold



Do you have questions about this process? Get in touch with Polytek Technical Support:
Fill out our simple online contact form.

Tek-Tip: How Cold Weather Affects Polytek® Products

December 3rd, 2014

With temperatures dropping across the country, we would like to address how cold temperatures affect the following Polytek products:

  • Latex
  • Pol-Ease® 2601 Release Agent
  • Polyurethane Rubbers, Casting Plastics & Foams
  • Silicone Rubbers




Our latex-containing products: Poly Latex 60 & Poly Latex False Face Compound

Polytek Latex-01

Unlike the majority of our products, latex will freeze and become permanently unusable. In fact, we do not ship latex if temperatures are too low.

If you currently have latex in storage, make sure that temperatures do not drop below 40°F. Store at temperatures between 50ºF – 70ºF.

If you are making a latex mold in colder temperatures, it will slow the evaporation process.

For further technical information on using latex, view the Poly Latex 60 Technical Bulletin or Poly Latex False Face Compound Technical Bulletin.



Pol-Ease 2601 Release Agent

Pol-Ease 2601 Release Agent

Like latex, this water-based release agent (primarily used when casting plaster or concrete in rubber molds) will freeze in cold temperatures and become unusable.




Polyurethane Mold Rubbers, Casting Plastics & Foams


Polyurethane Rubbers and Plastics-01

 [product examples — left: EasyFlo 120 Liquid Polyurethane Plastic | right: Poly 74-24 Liquid Polyurethane Rubber]


Transporting liquid polyurethane products in cold temperatures will not affect them long-term, but these liquids should always be brought up to room temperature (60ºF – 90ºF) before use. Surface and air temperatures should be above 60°F during application and for the entire curing period. For best results, these products should also be stored at room temperature.

Mixing and using polyurethane products at low temperatures will increase viscosity and slow the pour and cure times. Polyurethanes are moisture sensitive, and extended cure times increase the likelihood of moisture contamination. Moisture contamination can cause improper cure of products and, in some cases, may prevent a product from curing entirely.



Silicone Rubbers


[product example — PlatSil® 73-20 Silicone Rubber pictured above]


Similar to polyurethanes, transportation in cold temperatures will not have any long-term impact on liquid silicone rubber. For best results, they should be stored at room temperature (60ºF – 90ºF).

Before mixing and using silicone, always bring the liquid back up to room temperature (60ºF – 90ºF). Working with liquid silicone rubbers at low temperatures will increase the viscosity and slow the pour and cure times (this delay is especially noticeable in platinum silicone rubbers).


Making a mold of a frozen model? Try an accelerated, tin-cured silicone rubber like TinSil® 70-30 or TinSil® 80-30 with TinSil FastCat Accelerator.


Do you have questions about your upcoming mold making or casting project? Get in touch with our technical support team:
Fill out our simple online contact form.

Tutorial: Silicone Blanket Mold with Foam Mold Shell

November 26th, 2014

This tutorial features the making of a poured blanket mold (for general information on blanket molds, visit this “blanket mold: basics” blog entry).

Unlike brush-on blanket molds, where the mold shell is created after the rubber mold is made, the poured blanket mold technique requires that the mold shell be created before the rubber mold is poured.

There are many mold materials and mold shell options available for this mold making method. For this tutorial, PlatSil® 73-40 Silicone Rubber is selected as the mold material and PolyFoam R-5, a rigid casting foam, is selected as the mold shell material.

The model, pictured below, is a skull and bones prop composed of sealed plaster.

Skull and Bones Blanket Mold 004


Step One: Apply Uniform Layer of Clay to Model

Prior to creating a layer of clay on the model, we recommend outlining the perimeter of the model with a marker or pencil – the model will need to be placed back in this position later in the process and this will help to re-position it.

Cover the model with plastic wrap; this will make removal of the clay easier in later steps:

Skull and Bones Blanket Mold 006

Apply a uniform layer of clay over the model at about 1/2″ thick. We are using plasticine clay, an oil-based and sulfur-free clay. It is important to use a sulfur-free clay as sulfur can inhibit platinum silicone rubbers.

Skull and Bones Blanket Mold 008

Carefully cover the entire model and also extend the clay beyond the model to create a flange (~1.5″ long).

Skull and Bones Blanket Mold 010

Smooth the clay as best as possible; a tongue depressor works well for this process. The mold rubber will eventually take the place of this clay, so it’s important to make sure that there are no thin spots or holes in the clay, as they will also appear in the rubber mold.

If you intend to cut the finished mold, you should consider creating a raised clay parting line – this will create a thick area in the finished rubber mold that will allow for a better cut.

This is also the point in which you should build clay parting lines if you intend to create a multi-piece mold shell (see this example here). In this case, only a one-piece shell is necessary and a cut will not be made in the mold, so no parting lines are created.

Skull and Bones Blanket Mold 014


Step Two: Construct Mold Box

This step is not always necessary. We often utilize thickened liquid plastic (e.g., Poly 1512X Liquid Plastic + PolyFiber II) to make mold shells (example here) – a mold box is not required when using thickened liquid plastic because it generally strong enough on its own and does not need to be “contained”. In this example, we are using a rigid casting foam (a less expensive option compared to plastic) to create the mold shell. Because this foam expands, it needs to be contained by a mold box. The mold box, which will become a permanent fixture in the mold shell, also provides strength during the casting process.

Several pieces of wood are glued and screwed together to form a shape similar to that of the model. It should be designed so that the edges of the clay flange surrounding the model meet the interior edges of the mold box.

>Skull and Bones Blanket Mold 016

Skull and Bones Blanket Mold 017

Place the model and mold box onto a baseboard (we use a piece of melamine-laminated particle board) and secure it from underneath with wood screws.

Ensure that the clay meets the interior edges of the mold box.

Skull and Bones Blanket Mold 019

Mark reference points for the position of the mold box compared to the baseboard so that it can be re-positioned in the same location later in the process. Marking the entire perimeter of the mold box with a marker or pencil is also a good idea.

Skull and Bones Blanket Mold 024


Step Three: Apply Sealers & Release Agents

In this case, we want the foam to stick to the wooden mold box so it becomes a permanent part of the mold shell, so we do not apply any release agent to the wood. Paste Wax is applied to the plasticine clay so that the foam does not stick to it.

Skull and Bones Blanket Mold 027

Step Four: Cast the Foam Mold Shell

PolyFoam R-5, a rigid polyurethane casting foam with a free-rise density of 5 lb/ft³, is selected as the mold shell material. To cast the foam shell, cover the top of the mold box walls with another piece of laminated particle board (we apply Paste Wax to bottom of the lid before securing it to the mold box walls). This piece of particle board should have a pour hole in it. Secure the lid to the mold box walls (e.g., wood screws, mold straps) and then prepare to mix the PolyFoam R-5.

PolyFoam R-5 has a 1A:1B mix ratio, a cream time of 30 seconds, a rise time of 3 minutes and a demold time of 30 minutes. It is best to mix foam with a Turbo Mixer or other high-speed mixer.

Mix for approximately 15 seconds and then pour the foam into the pour hole of the lid; PolyFoams being to rise quickly, so it is important to work fast.

Skull and Bones Blanket Mold 029

Skull and Bones Blanket Mold 030


Wait ~30 minutes before carefully removing the lid.

Skull and Bones Blanket Mold 033

Unscrew the the mold box, flip it over and remove the plastic wrap and clay from the model.

Skull and Bones Blanket Mold 035

Skull and Bones Blanket Mold 037


Step Five: Make Pour & Vent Holes in Mold Shell

Create a pour hole (large enough to pour the mold rubber into) and vent holes where necessary; we made one vent hole in each skull cavity. A hole saw or drywall saw work well.

Skull and Bones Blanket Mold 038


Step Six: Test, Measure, Mix & Pour the Silicone Mold Rubber

PlatSil 73-40 Silicone Mold Rubber is selected to make the mold. It is a platinum-cured silicone rubber with a 1A:10B mix ratio, a Shore A40 hardness (similar to the hardness of a pencil eraser), a 45-minute pour time and a 16-hour demold time.

This plaster model was, at one point, in contact with a material that can sometimes inhibit the cure of platinum silicone rubber, so we do a small test cure on the surface to ensure proper cure (read more about test cures here) before pouring the entire mold.

Skull and Bones Blanket Mold 039

Place the model in it’s original position on the baseboard using the perimeter marks you made earlier.

Spray Pol-Ease® 2500 Release Agent onto the model and brush out with a dry brush.

Pol-Ease2500_Release Agent

Place the mold box/foam mold shell over top of the model in the proper position (line up the “A” side of your mold box with the “A” on the baseboard and follow perimeter marks) and screw it into place. It is also a good idea to “seal” the exterior edges of the mold box (where it meets the baseboard) with clay to prevent rubber from potentially leaking.

At this point, there will be an empty cavity in the space that the clay once filled.


How to measure how much silicone is needed:

The volume of clay removed from the model equals the volume of liquid rubber needed. Calculate the volume of clay by multiplying its weight by its specific volume:

For instance, if 8 lb of clay was removed from the model: 8 lb x 18.4 in³/lb (the specific volume of the clay) = 147.2 in³ of clay.

Next, divide the clay volume by the specific volume of the liquid rubber to get the weight of rubber needed:

147.2 in³ ÷ 22.0 in³/lb (the specific volume of PlatSil 73-40 Silicone Rubber) = 6.69 lb of PlatSil 73-40 Silicone Rubber


Pour the silicone into the pour hole of the foam shell; small amounts of silicone will rise from the vent holes.

Skull and Bones Blanket Mold 040

Allow 16 hours before demolding. Unscrew the mold box walls/shell from the baseboard and lift it off of the model. Your silicone blanket mold with foam shell is complete!

Skull and Bones Blanket Mold 045
The rubber mold picks up every detail from the original model.

Skull and Bones Blanket Mold 046



A variety of materials can be cast in a PlatSil 73-40 silicone mold, many of which don’t require a release agent. This includes polyester, epoxy, wax, concrete, plaster, and polyurethane resins and foams.

In the example before, we brush Poly 1512X Liquid Plastic with PolyFiber II into the mold.

Skull and Bones Blanket Mold 049


Here is the plastic casting after being painted:

Do you have questions about your upcoming mold making or casting project?
Fill out our simple online contact form.

Tutorial: Brush-On Rubber Mold of Decorative Architectural Element

November 18th, 2014

The following tutorial features the making of a one-piece, brush-on Polygel® 35 polyurethane rubber mold and a two-piece Poly 1512X Liquid Plastic mold shell.

The purpose of the mold is to later cast concrete copies of this decorative architectural piece.

 Plaster Model for Mold Making

Mold Making with a Plaster Model


Step 1: Prepare the Model

This model is composed of painted plaster. Because the plaster is already sealed with paint, additional sealing agent is not necessary. A release agent is required to prevent the polyurethane rubber from sticking to the model, so Pol-Ease® 2300 Release Agent is sprayed onto the model and surrounding baseboard and then brushed out with a dry brush.

This particular release agent is being used because a polyurethane mold rubber is going to be applied to the model. If a silicone mold rubber was selected as the mold material, a different release agent would be recommended (i.e., Pol-Ease® 2500 Release Agent). For more information on Polytek release agents and sealers, view our Sealer & Release Agent Selection Guide.

Pol-Ease 2300 Release Agent

Step 2: Brush On Liquid Mold Rubber

Polygel 35 Brush-On Rubber is selected as the mold material. Polygel 35 is a self-thickening, two-part polyurethane rubber that cures to a Shore A35 hardness. Upon mixing Part A & Part B (1A:1B mix ratio), the mix immediately thickens to a brushable consistency. It is a great option for those that would rather not add a separate thickener (i.e., all Polytek pourable liquid mold rubbers can be thickened with the addition of a separate thickener, like PolyFiber II).

Because there are no major undercuts on this model and Polygel 35 is a relatively soft rubber, a one-piece mold can be made. One-piece blanket molds that can be lifted or peeled off of models without a cut in the mold are often referred to as “glove” or “sock” molds.

Generally, blanket molds should be between 1/4″ and 3/8″ thick, which requires multiple layers.

Carefully apply the first layer of Polygel 35, making sure that all of the details of the model are filled with rubber. Also create a flange of rubber around the model on the baseboard (we often use melamine-laminated particle board as baseboards, like the example below).


Brush-On Polygel Rubber

Before applying the second layer of rubber, allow the first layer to gel enough that application of the second layer will not disturb or move it. This takes about an hour, depending on temperature and humidity.

To ensure uniform coverage of each layer, a small amount of PolyColor Dye can be mixed into the Polygel so that thorough coverage can be checked visually. In this example, Red PolyColor dye is added for application of alternating layers:

Polygel 35 Brush On Mold Rubber

Polygel 35 - Second Coat Finished

Allow the second layer to gel before applying the third layer.

Polygel 35 Mold Making Rubber

Allow the third layer to gel before applying the fourth, and final, layer of rubber.

Polygel 35 - Final Coat

Allow the rubber to cure for 8-12 hours at room temperature before constructing the mold shell.


Step 3: Construct Mold Shell

Poly 1512X Liquid Plastic is selected to construct the two-part mold shell. Poly 1512X has a 1A:1B mix ratio, a short working time of ~5 minutes and a demold time of ~30 minutes.

In this example, the parting line will run vertically down the middle of the “face” – it’s important to be aware of undercuts that could potentially lock the mold shell onto the model and mold.

Shims can be created from a variety of materials (e.g., metal flashing, plastic) – cardboard is used for this example. Make an outline of the shape of of the mold with a marker and then cut the shape out.

Draw Cutout for Shim

Place the shim over the designated parting line.

Place Shim over Model and Mold

To help prevent the plastic shell material from leaking onto the other side of the mold, caulk the edges with plasticine clay. Although it is not shown in this example, it is a good idea to place some clay “keys” on the cardboard shim in areas that will contact the shell material. This is done to register mold shell halves for improved alignment later.

Apply Clay to Edges

The mold rubber, cardboard shim and surrounding baseboard need to be coated in a proper release agent so that the polyurethane plastic shell does not bond. In this example, Paste Wax is applied with a brush and then Pol-Ease 2300 Release Agent is sprayed and brushed out with a brush.

Poly 1512X Liquid Plastic is a pourable plastic with a low viscosity of 400 cP (i.e., a viscosity similar to SAE 30 Motor Oil), so PolyFiber II thickener is added to the mixed resin to bring the plastic to a brushable consistency for application. Add PolyFiber II to the liquid plastic until a paste-like consistency is reached.

Polyurethane plastics cure faster in larger masses, so it’s important to work relatively quickly and get the plastic out of the mixing container and onto the mold. Dry brushesstainless steel spatulas, and Poly Paddles are good tools to use to move the plastic into position. Completion of half of a mold shell may require more than one batch of plastic, depending on the size of mold shell and how much plastic is being mixed at a time. If the shell requires a second layer, allow the first layer to gel before applying the second layer.

Make sure to create a mold shell flange that extends beyond the mold.

Construct First Half of Mold Shell

Wooden legs are added before the plastic completely sets. They are used to level the mold for casting later.

Wooden Sticks

Allow the first half of the mold shell to cure (the demold time is ~30 minutes; however, thin sections may take longer) and then remove the cardboard shim and prepare to make the second half of the mold shell.

Allow Plastic to Cure

Apply Paste Wax followed by Pol-Ease 2300 Release Agent to the Polygel 35 rubber, mold shell flange and surrounding baseboard. Also apply these to the opposite side of the mold shell flange in case any plastic accidentally spills over during application.

Apply Paste Wax

Construct the second half of the mold shell.

Construct Second Half of Mold Shell

Add the wooden legs at the same height as the opposite side.

Add Wooden Legs

Once the shell has completely cured, drill holes and insert hardware (e.g., bolts, washers, nuts) through the mold shell flange (not pictured here) to secure the two sides together for casting later.

Finished Plastic Mold Shell

Carefully pry the mold shell off of the baseboard using a putty knife or crowbar – it’s best to loosen all edges before removing the entire thing. The edges of the plastic mold shell will be very sharp, so sanding is recommended.


Your mold is now ready for casting!

As mentioned previously, this mold was designed for casting concrete; however, numerous casting materials can be poured into polyurethane molds. This includes plaster, waxes and resins and foams (with use of the proper release agents). For assistance in choosing an appropriate mold material, visit our website.

Pictured below: A painted EasyFlo 60 Liquid Plastic casting made in the Polygel 35 mold.


Plastic Architectural Element

Video Tutorial

The following video tutorial shows the poured blanket mold technique with a different model and mold material:

Do you need assistance in selecting a mold material, mold making method, or casting material? Contact us:
Fill out our simple online contact form.

2015 Polytek® Mold Making & Casting Seminar & Workshop Dates

November 11th, 2014

We have just announced the 2015 dates for our Mold Making & Casting Seminar & Workshop:


Join us for this two-day seminar and workshop on:

March 26 & 27, 2015


October 15 & 16, 2015






Polytek Workshop 80


For details on what takes place during this two-day seminar and workshop, visit the seminar information page on our website.


To read about some of our most recent seminars/workshops, visit the following blog entries:  October 2013  |  March 2014  | October 2014


For additional information, pricing, or to sign up, please contact us at 800.858.5990 or


We look forward to seeing you there!

New Catalog: Mold Making & Casting Materials for Sculptors & Foundries

November 3rd, 2014

Mold Making Materials for Sculptor and FoundriesGiven the amount of mold making and casting products available for sculptors/artists and foundries, it can be difficult to filter down the options when researching for a specific project. In our Mold Making & Casting Materials for Sculptors & Foundries catalog, we narrow down our large product line to a select group of materials that have proven successful for mold makers year after year.

This group of products includes polyurethane and silicone mold rubbers, casting plastics, release agents, and accessories.

If you have questions about your project after reviewing the catalog, please get in touch with us. Our technical support staff is available Monday through Friday, 8:30am – 4:30pm [EST] to answer your questions:
Fill out our simple online contact form.


How to Make Silicone Rubber Molds for Casting Wax Candles

October 29th, 2014

The following video tutorial features the making of three PlatSil® 73-25 Silicone Rubber molds to cast wax in to make candles. Two of the models used to make the molds are branches from a fallen tree. The third model is a plastic pine cone.

Candle Models

We cut the branches down to an appropriate size for candles:


Models for Candle Making

PlatSil® 73-25 Silicone Rubber is used to make the molds. It is a two-part platinum silicone rubber with a 1A:1B mix ratio, Shore A25 hardness, 20-minute pour time, and 4 to 5-hour demold time.


PlatSil 73-25 Silicone Rubber

The full tutorial is provided below, followed by a list of materials and tools used for the project:



  1. Select a Model
  2. Construct Mold Boxes & Prepare Models
  3. Measure, Mix & Pour Silicone Mold Rubber
  4. Demold
  5. Melt & Pour Wax
  6. Remove Candle from Mold





Materials & Tools Used

– Original Models
PlatSil® 73-25 Silicone Rubber
PolyPoxy® Quick Stick Epoxy Adhesive
Pol-Ease® 2350 Sealer & Release Agent
Pol-Ease® 2500 Release Agent
– OPTIONAL: EasyFlo 60 Liquid Plastic
– Wax, Wax Colors, Wick, Clamp for Wick
Dry Brushes
– Mixing Containers & Mixing Tools
– Mold Containers (e.g., PVC pipe, particle board, pail)
Plasticine Clay
Tongue Depressors
– Drill
– Screws
– Digital Scale
– Putty Knife/Crowbar
– Scalpel


Additional Tutorial

Click here for another candle-making tutorial based on a decorative glass object.


For more information on mold making supplies for candle making:

Call us at 800.858.5990.
Email us at
Fill out this simple online form.

Or leave a comment right here on the blog!

Mold Making & Casting Seminar & Workshop: October 2014

October 23rd, 2014

Last week, we held our fall Mold Making & Casting Workshop (see a recap of our March 2014 workshop here). Workshops are two days long and include the following:


  • Make your own molds and castings
  • One-on-one guidance from Polytek staff members
  • Work with a wide variety of mold rubbers and resins
  • Learn a variety of mold making and casting techniques
  • Meet others with similar interests
  • Buy material at low trial unit prices during the seminar


Attendees are invited to bring their own project to the workshop or choose from our large supply of in-house models.

For more details, visit the Polytek website.


Here are some photos from the workshop:

Mold Making and Casting Workshop


Demonstrations from Polytek staff members:

Polytek Workshop 1

Polytek Workshop 2

Polytek Workshop 3

Polytek Workshop 4

Polytek Workshop 11

Polytek Workshop 6

Mold making and casting photos:

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Polytek Workshop 65 (2)

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Polytek Workshop 100


Check the Polytek website for upcoming workshop dates or get in touch with us:

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Tutorial: How to Make a Silicone Rubber Candle Mold

October 15th, 2014

The following tutorial details the process of making a silicone rubber mold for casting wax to make candles.


Supplies Needed for Project:

Rubber Molds for Candle Making


Step 1: Select a Model

Select or create a model to replicate. The final wax candle will be a copy of this original model. Many candle makers sculpt their original models with clay, wood or wax or utilize computer-based options like 3-D printers and CNC routers to produce their designs.

The model that we selected for this particular project is made of glass:


Glass Object for Making Mold


This glass model is hollow; however, we would like the final candle to be solid, so we fill the model with wood and clay:


Inserting Wood

Wood Inserts

Fill Model with Clay


The mold rubber will pick up every detail of the model, so the clay is carefully smoothed out:


Even out Clay

Smooth Clay in Model


Step 2: Construct a Mold Box & Secure the Model

To make a one-piece poured block mold, construct a mold box or select a suitable container to place your model in. Make sure that there is enough space between the model and the mold box walls to create mold walls with an appropriate thickness.

We leave approximately 1″ of space for mold walls and the mold bottom in this example.

Plywood is being used to construct the mold box. Porous materials like this must be sealed prior to pouring liquid mold rubber. The plywood will be sealed in Step 3.

Some other possible options for mold boxes or mold containers: Plexiglas®, plastic pails, PVC pipe, Sonotubes®, melamine-laminated particle board (you can purchase a 24″ H mold box directly from Polytek).


Cutting Plywood for Mold Box Walls


Using a hole saw, we create a hole in the bottom board of the mold box to hide this part of the model (we do not want this protrusion on the final candle):


Protrusion in Glass


Cutting Hole in Wood

Hole in Plywood


Securely adhere the model to the bottom board so it does not float when the mold rubber is poured around it.

Using PolyPoxy®  Quick Stick Adhesive, a two-part, fast-setting epoxy adhesive, we adhere the model to the bottom board:


Epoxy Adhesive for Mold Making


PolyPoxy® Quick Stick Adhesive has a 1:1 mix ratio and sets in 3-5 minutes.


Apply Epoxy Adhesive

Adhere Model in Bottom Board with Epoxy

Model on Baseboard (2)


While the epoxy is curing, construct the walls of the mold box:


Construct Mold Box

Construct Plywood Mold Box

Finished Mold Box


Step 3: Apply Sealer & Release Agents as Necessary & Finish Preparing the Model

Apply appropriate sealers and/or release agents to the mold box.

As mentioned previously, the plywood used for this mold box is not sealed. We coat it with Pol-Ease® 2350, a white petrolatum dissolved in mineral spirits, which serves as both a sealer and release agent. No additional release agent is necessary.

When using a non-porous mold box, consider applying Pol-Ease® 2500 Release Agent instead (Use this option when working with silicone rubber. Use Pol-Ease 2300 Release Agent when working with polyurethane rubbers).

Not sure which release agent to use for your particular project? Our Sealer & Release Agent Selection Guide may be helpful.


Pol-Ease 2350 Sealer and Release Agent

Apply Sealer to Mold Box


Apply a release agent to the model.

We also apply Pol-Ease 2350 Sealer & Release Agent to the model itself. Pol-Ease® 2500 Release Agent (an aerosol spray) is another option that could be used in this case (for use with silicone mold rubbers).


Polytek Sealer and Release Agent


Allow sufficient time for the solvent in Pol-Ease 2350 to evaporate (~1 hour, depending on temperature and humidity) before moving on to the next steps.

Seal any areas around the model where rubber may leak. There are small gaps at the base of this model, so we seal that area with plasticine clay (warmed up for easier application). Other options for sealing include caulk and hot glue.


Clay Snakes


Smooth and flatten the clay as best as possible:


Smooth Clay

Clay Caulking


Place the model in the mold box and secure the bottom board to the mold box walls:


Assemble Mold Box

Secure Mold Box


Place the mold box and model in the proper position for pouring the liquid rubber:


DSC06980 - Copy


Seal the edges of the mold box with plasticine clay to help prevent rubber from leaking outside of the box:


Clay Snakes - Caulk Box

Mold Box Sealed with Clay


Step 4: Measure, Mix & Pour Silicone Rubber

The mold rubber selected for this particular project is PlatSil® 73-15 Silicone Rubber.

Basic Specifications for this Rubber:

  • Type of Silicone: Platinum-Cured
  • Mix Ratio: 1A:1B
  • Shore Hardness: A15
  • Pour Time: 20 minutes
  • Demold Time: 4-5 hours
  • Color: White Translucent
  • Mixed Viscosity: 2,500 CP


NOTE ABOUT CURE INHIBITION: Contamination from amines, sulfur, tin compounds, polyester resins, some 3D-printed plastics, and some other materials can cause cure inhibition in platinum-cured silicone rubbers, so ensure that your model and other materials coming into contact with the silicone do not contain these inhibitors. It is best to perform a small test cure on your model before pouring a large mold.

This particular mold requires approximately 10 lb of PlatSil 73-15 rubber (5 lb of Part A & 5 lb of Part B).

PlatSil 73-15 Silicone Rubber for Candle Making - Polytek

Weigh out Part B on a digital scale – we recommend pouring Part B first because it is lower in viscosity than Part A and is less likely to cling to the sides of the mixing container:
Part A of PlatSil 73-15 Silicone Rubber

Tare the scale and weigh out Part A into the same mixing container.
Part B of PlatSil 73-15 Silicone Rubber

Thoroughly mix Part A and Part B together, scraping the sides and bottom of the mixing container several times:
Mix Silicone Rubber Thoroughly

Carefully pour the mixed rubber into the mold box. Pour into one corner and allow the rubber to rise. Do not pour rubber directly onto the model:
Pour Silicone Rubber into Mold Box

Soft Silicone Rubber

Allow Silicone Rubber to Cure

PlatSil 73-15 can be demolded in 4 to 5 hours at room temperature. If a different rubber is being used, make sure to check the demold time of that particular rubber. Demolding too soon can cause permanent warping of the mold.

Step 5: Demold & Cut Mold (if necessary)

Carefully remove the mold box bottom board and walls. A putty knife may be helpful in this process:

Remove Mold Box

Remove Mold Box Bottom Board

Carefully Remove Mold Box

Remove Wood and Clay

Depending on the shape of the model, the mold may have to be cut to remove the model and subsequent castings. We use a scalpel to cut an irregular pattern on one side of the mold (irregular patterns realign better for casting than straight cuts):
How to make a cut in Silicone Mold

Make Irregular Cut in Mold

Carefully remove the model from the mold:


Polytek Silicone Mold

Finished PlatSil 73-15 Silicone Candle Mold

Make a small hole in the bottom of the mold to later accommodate a wick:
Make Hole in Rubber Mold for Wick

This next step is completely optional. Before we move on to casting wax, we make a plastic copy of the original model just in case we need to make more molds at a later date (we broke the original glass model when demolding).
Wooden boards and duct tape are used to support the mold when casting (you could also use the original mold box for support):
Prepare Mold for Casting Plastic

EasyFlo 60, a fast-setting polyurethane plastic, is poured into the mold to make the copy:
Casting EasyFlo 60 Liquid Plastic

This plastic can be demolded in 15-30 minutes:
Plastic Copy of Candle

EasyFlo 60 Decorative Element


Step 6: Pour Wax into Mold

Feed a wick through the hole created earlier:


Place Wick in Silicone Mold

Candle Making with Silicone Mold

Temporarily tie a knot in the wick:
Knot in Wick

Wick in Silicone Mold

Secure the wick above the pour hole of the mold. Make sure it is centered:
Suspend Wick for Wax Casting

Secure Wick with Clip

Melt wax with the appropriate equipment and add dyes and fragrances if desired:
Wax in Parrafin Bath


Carefully pour the wax into the mold:
Casting Wax in Polytek Silicone Mold

Allow Wax to Cool in Silicone Mold

Allow the wax to completely cool:
Demold with Wax is Cooled


Step 7: Remove Candle from Mold

Carefully remove the candle from the mold:

Remove Candle from Mold


Trim the wick as necessary:
Trim Wick on Both Ends

Hundreds of candles can be made in this single mold. A finished candle is pictured below:
Decorative Candle from Silicone Mold

Close-Up of Candle Detail from Mold

Candle Making Tutorial


We utilized a soft, silicone rubber for this tutorial; however, polyurethane rubbers are also a viable option for candle making. Some waxes perform better in silicone molds vs. polyurethane molds. Please get in touch with us to discuss your specific candle-making project:

Call us at 800.858.5990.
Email us at
Fill out this simple online form.

Or leave a comment right here on the blog!

Warping Decorative Concrete Elements in Rubber Molds

September 30th, 2014

Last week, we posted a video tutorial on making a rubber mold to cast “warped” side-by-side concrete tables. Our latest tutorial (below) focuses on casting “warped” decorative concrete elements in Poly 74-20 polyurethane molds. The original model was constructed through a series of steps involving wood, silicone rubber (PlatSil® 71-10), and polyurethane casting resin (EasyFlo 60).

The finished concrete elements can be used for a variety of purposes: tables, light housing, planters, garden decor or trellis, decorative panels (when cast flat), and much more.


For more information on liquid rubbers that can be used to make molds for warping concrete:

Call us at 800.858.5990.
Email us at
Fill out this simple online form.

Or leave a comment right here on the blog!