Q & A: Platinum Cured Silicone Rubber (19 comments)

This is the first time I have made my own silicone mold. Although the surface has solidified to the touch, some parts of the side that are in contact with the skull are still sticky. I waited for more than 24 hours and it is still sticky. Can I solve this problem?

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What material is your skull model made of? Some materials will inhibit the curing of platinum-cured silicone. Although the surface may appear dry, the inside may still be sticky.

This is my first time using silicone to make molds, and so far, the results are great. I didn't use any release agent and the casting came apart easily. Also, I did not vacuum degas the silicone. After the liquid silicone sits for a while, all the air bubbles will rise to the top. I also tried applying heat to make it cure faster but the results were terrible with lots of bubbles. So just letting it sit at room temperature seems to work well. One thing to note, however, is that most SLA resins appear to be incompatible with platinum-cured silicone, inhibiting its proper curing.

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If you cannot drain all the air bubbles, you can punch holes at high points in the top half of the mold to allow the air to escape. You can make them large enough to put a funnel or straw in the hole to hold the excess silicone while you fill it with the caulk tube (assuming that's how you fill it). For surfaces where the 3D-printed resin model is not compatible with platinum-cured silicone, spray it with clear wood lacquer. We use this method every day to make silicone molds from SLA castings.

I've been using condensation-cure silicone, but now I'm keen to explore addition-cure silicone. I understand that addition-cure silicone can cast more products compared to condensation-cure silicone.

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I don't believe that addition-cure silicone allows for more casting instances than condensation-cure silicone—it depends on the casting materials used. Compared to condensation-cure silicone, addition-cure silicone has a lower shrinkage rate, which is what I've discovered so far.

I have been in pursuit of food-grade silicone for crafting artisanal chocolates. Indeed, the blending process tends to introduce air bubbles, yet pouring the mixture delicately and steadily from a height helps prevent the formation of bubbles on the mold. Additionally, I believe employing a fine brush to apply silicone within a limited area before pouring is a prudent practice. As for the release agent, I delicately brush on a thin layer of clarified butter.

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Platinum-cured silicone, an odorless and non-toxic material, holds FDA certification, ensuring its safety for food contact. Your recommended method for minimizing bubbles is indeed a valuable technique.

We have encountered an issue in replicating prototypes using clay, specifically with insufficient solidification on the clay surface. Despite meticulously cleaning the prototype and making a renewed attempt at replication, the outcome persists unchanged. The crucial mold segment remains in a state of viscous resistance, resisting solidification. No coatings have been applied to the clay, yet it appears that the clay's constituents are hindering the curing of the RTV-2 liquid silicone rubber.

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Platinum-cured silicone, featuring a platinum catalyst, experiences hindrance in solidification when in contact with sulfur-containing clay. It is recommended to employ clay devoid of sulfur to accomplish your project.

The platinum-cured silicone I utilized failed to solidify, remaining uncured even after 24 hours, particularly in areas that came into contact with the oil-based clay. Incidentally, this clay is from MR Hobby.

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Yes, platinum-curing silicone may encounter curing challenges when exposed to substances containing acids, alkalis, sulfur, and the like, leading to an inability to solidify. It is advisable to opt for sulfur-free clay in such instances.

In winter, the surface is still sticky even after 24 hours and is not fully cured. In summer, it starts to harden in about 15 minutes. It seems that it should be used at 23℃-25℃.

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Absolutely, temperature stands as a pivotal factor influencing the solidification pace of room-temperature vulcanizing silicone.

When crafting molds using 3D-printed resin prototypes as master models, I encountered curing failures at the surfaces in contact with the master model. I pondered whether this issue stemmed from insufficient drying of the UV resin prototype or a mismatch in components, given that the curing process was successful in areas other than the contact surface.

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Indeed, when platinum-cured silicone comes into contact with incompletely cured UV resin, it fails to solidify properly.

Can silicone be employed inside the mold after its fabrication?

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Certainly. When fully cured, silicone molds are versatile enough to cast an extensive array of materials.