Making molds with tin-cure silicone is like baking a cake. You need the right stuff and the right steps. If you do it wrong, the cake, or the mold, can get smaller! This is called shrinkage. We don’t want that! So, we will learn to make silicone molds with minimal shrinkage.
What is Tin-Cure Silicone?
Tin-cure silicone is one of silicone rubber types. It starts as a liquid, like milk. Then you add a special helper, called a curing agent. This makes it turn hard, like clay. This is good for making molds for things like toys, soaps, and fancy wall decorations.
Why Do Molds Shrink?
When tin-cure silicone goes from liquid to solid, it can get a little smaller. Think of it like drying clothes. Wet clothes are bigger, and dry clothes are smaller.
Tin-cure silicone shrinks more than another kind called platinum-cure silicone. Tin-cure can shrink about 0.3% to 0.5%. Platinum-cure shrinks only 0.1% to 0.2%. If your mold shrinks a lot, it will not match the model.
How to Make Molds Shrink Less
Here are some easy steps to learn to be better at reproduction molding4.
1. Use the Right Amount of Helper!
The curing agent is like salt in cooking. Too much salt can make the food bad. With tin-cure silicone, too much curing agent makes it shrink more. We need a perfect solution, which is like a well-balanced recipe, for reproduction molding .
- Use LESS than 4% curing agent.
- If you use more, the mold will shrink more.
2. Pick the Right Silicone
Some tin-cure silicones are made to shrink less.
- Topsil Silicone with EU standard catalyst shrinks very little. It is good for making strong molds.
- Mold Max 60 also shrinks very little. It is good for casting things like metal.
- Mold Max XLS 11 shrinks a little bit more, because it is a ‘water white transluscent’ rubber.
| Silicone Type | How Much it Shrinks | Good For |
| Topsil Silicone with EU standard catalyst | Very Little | Molds for many things, architectural restoration |
| Mold Max 60 | Very Little | Molds for metal |
| Platinum-Cure Silicone | Even Less | Molds that need to be very, very exact |
3. Make Thin Layers
If you make a cake, you put it in the oven in layers. Tin-cure silicone is the same.
- For Topsil Silicone, make four thin layers5.
- Thin layers help the mold dry evenly, keeping the shape you will use for architectural restoration applications 5.
4. Be Careful with Quick-Dry Helpers
There are addative helpers, such as Accel-T®, that makes the silicone dry fast. But be careful!
- Accel-T® makes the silicone dry fast, but it can also make it shrink more4.
- It also makes the silicone get thick faster. You have less time to work with.
5. Use a Good Master
When you make a copy of something, you need a master. Making a master is good for any home craft, or hobby!
- For tin-cure silicone, it is good to use a master made of epoxy resin.
- Also, a master made for platinum-cure casting provides a good stable shape3.
6. Keep Molds in a Good Place!
Even after a mold is made, it can keep shrinking a little bit over time8.
- Because, of the chemical reaction, byproducts are released1 in condensation-curing.
- Store molds in even temperature and humidity3.
7. A Different Way: Platinum-Cure Silicone
If you need a mold that shrinks almost not at all, use platinum-cure silicone3.
- Platinum-cure silicone shrinks much less than tin-cure silicone3.
- This makes it a good option for furniture mold making.
- It is good for things like making very small, exact parts.
Mistakes to Avoid
- Don’t use too much curing agent! Keep it below 4%3.
- Don’t rush! If you use a quick-dry helper, work fast but be careful.
- With correct silicone A:B ratios, you create the best conditions to reduce shrinkage2.
Putting it All Together
Here is an easy to read table that includes the main topics, with some extra information.
| Topic | Detail | Importance |
| Curing Agent | Use less than 4%3 | Too much makes the silicone shrink more. |
| Silicone Type | Topsil Silicone and Mold Max 60 are good choices | Some silicones shrink less than others . |
| Layers | Make thin layers | Helps the silicone dry evenly. |
| Quick-Dry Helpers | Use carefully; they can make the silicone shrink more | Good for speed, but can cause problems. |
| Master Material | Epoxy Resin Molds | Gives a stable shape for accurate casting |
| Storage | Even temperature and humidity! | Keep your molds in a good place, so they don’t shrink later. |
| Platinum-Cure | A different type of silicone that shrinks very little | Great for best furniture mold making |
| Avoiding Mistakes | Don’t use too much curing agent | Avoid shrinkage |
| Pouring Technique | Pour slowly into the lowest part of the mold, letting the material flow naturally | Helps reduce air bubbles and ensures even distribution of silicone |
Summry:
Making tin-cure silicone molds that don’t shrink too much is easy if you follow these steps. Remember:
- Use the right amount of curing agent.
- Pick a good silicone.
- Make thin layers.
- Be careful with quick-dry helpers, like Accel-T4.
If you do these things, your molds will be great! You can use the molds in your home craft or hobby8.
Internal Links
- For making fancy furniture molds, see our guide on Silicone for Furniture Mold Making.
- If you need help with reproduction molding, see our guide on Silicone for Architectural Restoration Molding.
- Are you interested in silicone in crafts?, see our guide on Silicone for Home Crafts & Hobbies Mold Making.
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