Why Silicone Molds Discolor and How to Fix

For resin crafters and small businesses, silicone molds can be considered high-frequency items. Some people may find that silicone molds discolor after being used for a while, mostly turning white or yellow, causing concerns about subsequent use and production. Today we will explore this problem and give practical solutions. Let's get started!

 

All Silicone Molds Have A Lifespan

Before we get to the point, we need to know that all molds have a "life". They don't last forever. Silicone molds will be discolored or damaged after so many uses. The length of time each mold lasts is dependent on a variety of factors, but poor silicone quality is the #1 reason they wear out quickly.

Why Silicone Molds Discolor?

The discolored parts are where the silicone has been broken down and depleted in the mold. The most common factors that cause discoloration of silicone molds are:

1. Mold Quality.

The life expectancy of a mold could be anywhere from 10 casts to 200 casts before your mold dies a natural death. Cheap molds are always made of garbage silicone to save money and they usually don't last long. The better the quality of the mold, the more times it can be used. Thicker molds will also help.

2. Alcohol.

Alcohol will break down resin and many people use it for easier residue cleaning on the silicone molds. However, alcohol is also one of the solvents that will actively work to break down the silicone. Prolonged use of alcohol straight into a mold will discolor and ruin the mold over time.

3. Heat.

Silicone can withstand temperatures up to 250°C (480°F). But prolonged use of heat can make silicone more susceptible to denaturation and discoloration. For example, resin releases heat during curing. Silicone will gradually wear down with use from the heat resin generates. If you tend to use torches or flame to burst bubbles in the resin, they can put out temperatures up to 1500°C (2730°F) that is far more than the molds can handle.

4. Sunlight/UV Light.

Sunlight or UV lights will dry out the silicone. Your mold will crumble and discolor sooner with direct exposure to sunlight/UV light.

How to Fix the Silicone Molds

Some said when a mold gets white it is finished. Hate to say this but it's true. Unfortunately there's no way to fix the mold and make it return to its original state. However, the good news is this doesn't mean you can't use the mold anymore. Usually, the finished pieces out of the mold can still maintain quality. You don't have to dump the mold yet. But if the mold has turned yellow, you need to pay attention to whether the yellow color will transfer to the cured resin and ruin the finished pieces. There's a chance that the clear resin part in your project will become yellow and ugly because of the yellowed mold.

How to Extend the Lifespan of Silicone Molds

Although there's no way to fix the discolored molds, we can still do something to extend the life of the molds before they discolor.

1. Buy quality molds.

Make sure you're buying quality molds from mold makers, rather than cheap molds from Aliexpress/Wish/Temu/etc. Only the better quality of molds you can use more times. If you have budget, buy handmade molds instead of machine made molds. Most of the handmade molds are made of platinum silicone that are thicker and high-quality. You can get much more casts and gorgeous unique details from handmade molds.

2. Use correct resin.

Make sure you're using the correct resin for the application, as overheating resin from exceeding the pour depth will degrade the molds faster via heat. When you pour a deep mold, use deep-pour resin instead of the usual resin you use. You might have seen the power of flash cure. That level of heat is a disaster for the molds.

3. Always use a mold release.

Try a release spray before you pour you next molds. Use a mold release spray made specifically for that purpose (not baby oil, vaseline, etc). A good mold release doesn't just help release the product, it conditions and maintains the silicone. When using the mold release spray, you can still paint your pigment on certain areas in the mold before pouring resin. But spray first then the paint.

We recommend the popular Mitreapel Silicone Mold Release Spray. It works wonders keeping silicone molds like new and increasing the life. It sprays on very smooth and even. Just a light coat and the resin pieces slip quite easily from the molds.

4. Don't use torch to remove bubbles.

If you use a torch or flame to remove bubbles, there's a chance you're melting the molds, especially when the opening is not big and the flame might touch the silicone.

5. Carefully clean your molds.

Never use solvents to clean your silicone mold, such as alcohol or acetone. Although these products make it easier to clean, they actively work to break down the silicone. For machine made molds, warm water and dish soap is your best friend here. You can also use tapes or alcohol free baby wipes to clean the residue on the molds. For handmade molds with crystal shine effect, please only use tapes to clean them.

6. Use silicone oil to condition molds.

You would be amazed on how well molds perk up after being rubbed with silicone oil, place in Ziploc bag and set overnight. Silicone oil is amazing for prolonging molds. It's usually added to acrylic paint to create cells in pour painting. Just put a few drops of silicone oil in the mold you have cleaned, and rub it around with a gloved hand. Add more if needed. You can wash them with a mild detergent and warm water if you're worried there is leftover oil.

We love to treat molds with Pouring Masters silicone oil from U.S. Art Supply. It comes with a dropper and dries quick with no residue. It's like putting hand lotion on your hands. You can feel the difference in your molds after and get more life out of your molds.

7. Store molds flat and separately. 

Never stack or squish silicone molds together, as they begin to warp, and that warping causes microtears that degrade the quality of your molds. Stacking molds together will make the molds stick to each other and you need to force them apart, resulting in the silicone weakening.

8. Avoid direct sunlight/UV light.

Store your molds in a dry, cool area away from direct sunlight.

Conclusion

Silicone molds don't last forever, but there are things you can do to try and get more life out of your molds. Maintain them well so they won't be discolored easily. Hope you enjoy this post and share a comment below if you have any questions.