Frequently Asked Questions & AnswersClick on the image below to browse our new E-Book "Setting You Up For Success" for answers to all your mold making and casting questions as well as step-by-step tutorials for over 26 different projects! You can download your own copy here: ComposiMold Mold Making Guide (pdf format)
How do I figure out how much ComposiMold rubber mold making compound I need?
The critical information that you need to know for this calculation is the density of the ComposiMold. ComposiMold has a density of 1.2 grams per cubic centimeter or 0.7 ounces per cubic inch. In most cases approximately a 0.5 inch on the outside of your mold is good to provide mold support to your mold.
Start by figuring out the size of your part. The easiest way to estimate is to take the length, width and height dimensions as an estimate in cubic centimeters or cubic inches. To this dimension, add an inch to each dimension and find the total area of your mold (Or use the volume of your container that you will be molding the part in) Subtract the part size from the container size and multiply by the density of the ComposiMold. This will give you the amount of ComposiMold you need. Here is an example from one interested customer:
The part to be molded is 4.5 x 6 x 0.5 inches. I suggest about a 0.5 inch of ComposiMold around to provide support. So 5.5 x 7 x 1.5 inch container. 57.75 cubic inches of material minus the original piece 4.5 x 5 x 0.5=13.5 cubic inches. So 57.75-13.5 = 44.25 cubic inches. Convert to weight. ComposiMold has a density of 1.2 g/cc (0.7 ounces per cubic inch) so: 44 times 0.7 = about 30 ounces of ComposiMold to make this mold. ComposiMold is also nice because if you decide to make the mold bigger or use too much material, you can just reuse it later, so it is not just wasted unlike most mold making materials.
What is the easiest and safest method to melt ComposiMold?
The easiest way is to melt the rubber molds is in the microwave. Melt the ComposiMold by heating above 130 F. Microwave times will vary depending on the microwave used.
Microwave times will vary. Start melting the flexible rubber mold with short heating times until you understand how the microwave will heat the ComposiMold. We have found that for the 6 oz container, 30 to 60 seconds is typically long enough to melt the resin. After microwaving, stir and let the temperatures equilibrate throughout the molding compound.
The 16 oz container should be heated for 3 to 5 minutes. Start by heating in 1 minute intervals. Stir it after every minute or less to make sure all the material is heated evenly.
For the 32 oz container, 6 to 10 minutes is typically needed. The first time you melt ComposiMold, do it in 1 minute intervals: 1 minute of heating followed by 1 minute of stirring to equilibrate the temperature. As you see how your microwave works, you can adjust the times.
Container Size Microwave times (estimates-times will vary) 6 oz 30-60 seconds 16 oz 3 to 5 minutes, stir every minute 32 oz 7 to 10 minutes, stir every minute
Warning: The ComposiMold container WILL melt if overheated. Do not heat the container without the ComposiMold in it. Also, the ComposiMold WILL BE HOT. Be careful.
You can also use a double boiler to melt your ComposiMold. A double boiler consists of one container inside another container with water between them. The purpose of the double boiler is to keep the heat from getting above 212 F. Marbles or rocks work well to keep the ComposiMold container off of the bottom of the pot. If the ComposiMold container is on a stove top directly, the container will melt. Heat the resin until it is melted.
How does ComposiMold solidify?
ComposiMold solidifies when it cools to a flexible, rubbery, polymer. So to solidify, just let the part cool. To speed up to process, you can put your part in the refrigerator or use ice packs against your part. Do not submerge the ComposiMold in water to cool.
What happens when the ComposiMold get dirty? How do you clean the ComposiMold?
You can filter the ComposiMold of any particles or pieces. The Starter Kit includes a funnel and two filters to use if the ComposiMold becomes dirty from the casting materials. You can also purchase these accessories seperately through our online store.
- Place a filter into the funnel.
- Hold the funnel above a container that can withstand the hot ComposiMold.
- Melt the ComposiMold as previously discussed.
- Pour the ComposiMold through the filter and into a second container.
What are the advantages of using ComposiMold mold making materials over Silicone molds?
ComposiMold is a less expensive (definitely cheaper in the long run) rubber mold for plaster casts, plastic casts, and others. The rubber mold is much more forgiving in terms of allowing you to fix mistakes (Reheat or use a heat gun to heat an area). The silicone molds are typically longer lasting for single rubber molds, although after they start to go bad, you can not fix them or recast them. One of the initial ways we started using ComposiMold was for a backing to brush-on silicone mold making materials and polyurethane molds because you can use very little of the silicone mold material and reduce the mold making costs.
What types of Materials can be cast with ComposiMold?
You can use many casting materials in the ComposiMold rubber molds including:
A typical issue that may occur is if the casting material creates too much heat and melts the ComposiMold or the casting material is mixed incorrectly. It may not solidify.
ComposiMold melts at 130 F. Any casting that creates heats up to more than 130 F will melt the ComposiMold. There are many ways to get around this limitation. Examples include:
- Pouring in intervals so each pour only creates a little heat and the heat can dissipate
- Adding filler such as dry talc, other dry powders, wood chips, etc. to the casting material so there is less casting material to create heat
- Freeze or Cool the ComposiMold or PowerMold prior to pouring in the casting material. The heat during curing can sometimes be removed faster than the ComposiMold can heat up. This is a great way of doing candle wax and soaps.
- Using a brush-on mold making material such as latex, urethane rubber, or silicone to create a barrier. This also helps create molds that can last for many more castings. This allows 90-95% of the mold to be reused whiles still getting the benefit of longer lasting molds.
Can I use plaster in the ComposiMold mold?
- Cool the ComposiMold mold by sticking it in the freezer for a bit. This will make a firmer mold before pouring in the plaster. This will also help if you are using a stronger plaster that creates more heat when curing.
- Use a thicker plaster mix that has less water. This will also make a stronger plaster casting.
- Be sure to use a mold release-talcum powder, Vaseline or vegetable oil may work well for your plaster casts. If you do make any plaster casts, we would love to see what you make.
- For more information visit the Plaster or gypsum page,
- PDF tutorial on using ComposiMold for plaster casts
- Video of a plaster cast being made
Yes, plaster casting is well suited to ComposiMold. Using a reusable rubber mold material and a very inexpensive mold material (plaster) makes the entire mold making process very low cost. A couple of things you can do to make the ComposiMold and Plaster work well:
Can I use ComposiMold for polymer clay push molds?
Yes. I recommend using the PowerMold for polymer clay push molds because of the higher stiffness. Make the mold as you normally would using ComposiMold. Press in the clay to make the shape. If necessary, place the rubber mold into a container to provide stiffness to the rubber mold while pressing in the polymer clay. Please check the Clay Push Mold Using ComposiMold (pdf) tutorial.
Do you need a special mold release when molding with ComposiMold?
We sell a mold release that has worked well for us for mold making and casting, but many other mold releases also work well. Petroleum jelly (Vaseline), cooking spray, vegetable oil, mineral oil, and others will provide the necessary separation in your molds. With all mold releases, be sure to wipe off any excess material from your mold. The best bet for determining the effectiveness of a specific mold release is to experiment and that is also one of the major benefits to ComposiMold-try it and reuse it.
How long does it take for the ComposiMold Rubber Mold to solidify?
This depends on the shape and size of the rubber mold. The larger the mold size, the longer it will take. You can speed up the solidifying by putting the mold in a refrigerator or freezer or using an ice pack.
Bubbles are forming on my casting, what is causing this?
The bubbles could be caused by quite a few different things: If your original master part is not sealed correctly, bubbles may come out from the part. This is probably the cause if you are using plaster, clay, or wood as the master. To solve, seal the master first with several layers of polyurethane spray or wood sealers. Elmers-like glue (PVA glue) works well to seal parts. In some cases petroleum jelly can stop the air from escaping your original part and also act as a mold release.
We recommend using a 4-5% PVA with 95% water solution (1 t-spoon Elmer's glue with 1 cup water) on the original casting. This reduces bubble formation during mold making.
You may have too much mold release, so the interaction causes bubbles. This seems to happens quite a bit when you use a vegetable oil as a mold release, but other mold releases may have this affect. Be sure to wipe off any access.
You may have bubbles in the ComposiMold from bubbling in the microwave. It may be worthwhile to remelt the ComposiMold and let it cool at room temperature so the bubbles can rise to the top and escape.
Sometimes when you do the casting, bubbles form because the heat from the resin (polyurethane and even hotter for epoxy) melts the ComposiMold. You can reduce the amount of exotherm by adding fillers into the resin so the resin mass per volume is less. The filler also absorbs some of the heat. Some potential fillers include: plaster, sand, flour, microballoons, and fiberglass. Many specialty fillers are available.
You may be putting bubbles in when you pour the ComposiMold into the container. The best way to avoid this is to just pour gently into the lowest area of the mold so the ComposiMold rises up over the part. Be sure any holes are filled with the ComposiMold and you are not trapping air.
You can also do quite a few things to get rid of bubbles that are in your mold while the mold is still liquid:
- You can use a toothpick or other object to push out the bubbles. This works well in small cracks or under undercuts
- Before sticking the ComposiMold in the freezer to cool, let it sit out for about 10 minutes to let the bubbles rise to the surface.
- Vibrate the part by pushing on the sides or even better a back massager against the mold sides.
- You can also paint on a thin layer of ComposiMold over the areas where the bubbles are forming. If you let this cool, you can be sure the bubbles won't be against the master part.
How many times can you reuse the ComposiMold?
With care, there is no limit to the number of times you can reuse ComposiMold or PowerMold. The current record for the number of unique plastic molds made with the same ComposiMold rubber mold material is over 45 times. It has been certified to conform to ASTM D-4236 for more than 35 times. Making the molds consisted of melting the ComposiMold making a mold, casting plastic parts, and repeating the cycle. Below is an image of the first 25 parts cast.
What does "Conforms to ASTM D-4236" mean?.
ASTM D-4236 is a standard published by a subcommittee of the American Society for Testing & Materials.
- the material has been evaluated by a toxicologist for acute and chronic toxicity;
- the label names the ingredients identified as presenting a chronic health hazard, if any;
- a product presenting a chronic health hazard comes with safe use instructions.
LHAMA, the federal "Labeling of Hazardous Art Materials Act", governs hazard labeling nationally. Its intent is that art materials should be labeled to warn consumers of potential chronic (long-term or slow-emerging) hazards.
ComposiMold-LT conforms to ASTM-D-4236.
Why do I want to use ComposiMold to make molds?
Make Great Molds-Without the Cost
ComposiMold is a unique, innovative mold making material designed to enhance you mold making experience. The ComposiMold is a reusable rubber mold making material that can make many molds and castings with only one mold making material. ComposiMold provides a unique solution to sculptors and artists by allowing molds to be easily fixed by either using heat to reshape the mold or by re-melting the composite and starting the mold over.
The current record for the number of unique molds made with the same ComposiMold is over 40 times. For this test, the ComposiMold is melted, a mold made, a part cast, and the cycle repeated. Below is an image of the parts cast.
ComposiMold's rubber mold formulation provides a stable system with good mold strength, elongation of 150%, and longevity. ComposiMold is the easiest, flexible molding system available: melt, pour, and use. It is also important to note that no dangerous chemicals are used in the rubber mold and therefore safe for both the end-user and the environment.
ComposiMold's key advantage over other mold making materials is the fact that the product is reusable. Compared to other mold making products, ComposiMold has lower costs. Since the mold can be reused multiple times, the more you use the product, the more money you save. When learning to mold this is a very unique feature and when developing your castings, reusability of the rubber mold can provide dramatic savings.
Another advantage over competitors is that ComposiMold is safe for the environment. The composition of the product does not include petroleum or petroleum byproducts and if composted the material will biodegrade. Also, no dangerous chemicals are used during the production of the material.
ComposiMold is the easiest mold making material to use. The product is melted in the microwave and then used to create a mold of an original master piece. No weighing or mixing is necessary to complete the molding process.
ComposiMold is a rubbery, flexible resin mold made from a proprietary blend of environmentally friendly materials. Unlike most flexible mold making materials, ComposiMold is a thermoplastic resin that can be melted continuously.
A rubber mold is made by making a negative shape of an original master piece. This original master may be a figurine, action figure, toy, scientific instrument, sculpture, or any other piece you would like to mold. The melted ComposiMold is poured or painted onto the original and allowed to solidify by cooling. The time it takes for the ComposiMold to cool depends on the size of the mold. The master is then removed and the casting material is poured or pressed into the rubber mold cavity. You can make plaster casts, resin casts, plastic casts, and concrete casts. Casting materials may be polyurethane(urethane), silicone, epoxy, plaster, concrete, polymer clay, chocolate, or others.
Can I use ComposiMold to make molds of food?
Yes! ComposiMold-FC (food contact) is designed for use with foods.ComposiMold has been used for molding chocolates. It can also be used to make molds of foods (strawberries, bananna etc.) .
Can I get the MSDS for ComposiMold?
How hot is the ComposiMold when it is melted?
The ComposiMold rubber mold melts at 130 F. Do not go over 200 F.