Q & A: Platinum Cured Silicone Rubber (120 comments)
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2025-03-08
Emily
For a beginner, which silicone is easier to use?
It depends on what you mean by "easier." 1. For avoiding failure: Tin cure silicone is more "forgiving" as it is not easily "poisoned" or inhibited by common materials. This lowers the risk of failure for a beginner unfamiliar with material compatibility. 2. For simple mixing: Many platinum silicones offer a simple 1A:1B mix ratio by volume, which doesn't require a precise scale and is very convenient. Tin cure silicones often require a weight-based ratio (e.g., 100A:3B), which demands more accuracy. If a beginner is willing to learn about and avoid cure inhibition, a 1:1 platinum silicone can be simpler to handle.
It depends on what you mean by "easier." 1. For avoiding failure: Tin cure silicone is more "forgiving" as it is not easily "poisoned" or inhibited by common materials. This lowers the risk of failure for a beginner unfamiliar with material compatibility. 2. For simple mixing: Many platinum silicones offer a simple 1A:1B mix ratio by volume, which doesn't require a precise scale and is very convenient. Tin cure silicones often require a weight-based ratio (e.g., 100A:3B), which demands more accuracy. If a beginner is willing to learn about and avoid cure inhibition, a 1:1 platinum silicone can be simpler to handle.
2025-03-07
Harris
If platinum silicone is so good, when should I choose tin cure silicone?
Despite platinum silicone's superior performance, choosing the less expensive tin cure silicone is practical in several situations: 1. Very limited budgets: When cost is the primary driver. 2. One-off or short-term molds: If the mold will only be used a few times and doesn't need to be archived. 3. Low-precision projects: If a slight shrinkage of around 1% will not affect the final casting. 4. Masters containing inhibitors: If your original model contains substances known to inhibit platinum silicone (like sulfur-based clay) and cannot be sealed, using tin cure silicone avoids the risk of cure failure.
Despite platinum silicone's superior performance, choosing the less expensive tin cure silicone is practical in several situations: 1. Very limited budgets: When cost is the primary driver. 2. One-off or short-term molds: If the mold will only be used a few times and doesn't need to be archived. 3. Low-precision projects: If a slight shrinkage of around 1% will not affect the final casting. 4. Masters containing inhibitors: If your original model contains substances known to inhibit platinum silicone (like sulfur-based clay) and cannot be sealed, using tin cure silicone avoids the risk of cure failure.
2025-03-06
Phoebe
Can I make a mold of a 3D printed part? What should I watch out for?
Yes, but this is a major cause of cure inhibition. Many photopolymer resins used in SLA/DLP 3D printing contain chemicals (like photoinitiators or sulfur traces) that will prevent platinum silicone from curing. To succeed, the 3D print must be thoroughly post-processed.
Yes, but this is a major cause of cure inhibition. Many photopolymer resins used in SLA/DLP 3D printing contain chemicals (like photoinitiators or sulfur traces) that will prevent platinum silicone from curing. To succeed, the 3D print must be thoroughly post-processed.
2025-03-06
Ian
Is it safe to use platinum silicone for chocolate or cake molds?
Yes, but only if you use a platinum silicone that is explicitly labeled "Food Grade," "Food Safe," or is certified to meet standards like FDA 21 CFR 177.2600. These grades are tested to ensure they are non-toxic and won't leach harmful substances into food. Never use industrial-grade silicone for culinary purposes.
Yes, but only if you use a platinum silicone that is explicitly labeled "Food Grade," "Food Safe," or is certified to meet standards like FDA 21 CFR 177.2600. These grades are tested to ensure they are non-toxic and won't leach harmful substances into food. Never use industrial-grade silicone for culinary purposes.
2025-03-05
Lawrence
What materials can I cast into a platinum silicone mold?
Platinum silicone molds have excellent release properties and are compatible with a wide range of casting materials. You can cast polyurethane resins, epoxy resins, polyester resins, plaster, concrete, wax, soap, and various foams into them.
Platinum silicone molds have excellent release properties and are compatible with a wide range of casting materials. You can cast polyurethane resins, epoxy resins, polyester resins, plaster, concrete, wax, soap, and various foams into them.
2025-03-05
Rachel
Why is platinum silicone so sensitive to "cure inhibition"?
This phenomenon, also called "catalyst poisoning," occurs because the platinum catalyst is highly reactive but also very delicate. When it comes into contact with certain chemicals—notably compounds containing sulfur (S), tin (Sn), nitrogen (N), or phosphorus (P)—these substances bond to the catalyst and deactivate it. Once the catalyst is "poisoned," the addition cure reaction cannot proceed, leaving the silicone sticky and uncured where it touched the contaminant. This effect is permanent and irreversible.
This phenomenon, also called "catalyst poisoning," occurs because the platinum catalyst is highly reactive but also very delicate. When it comes into contact with certain chemicals—notably compounds containing sulfur (S), tin (Sn), nitrogen (N), or phosphorus (P)—these substances bond to the catalyst and deactivate it. Once the catalyst is "poisoned," the addition cure reaction cannot proceed, leaving the silicone sticky and uncured where it touched the contaminant. This effect is permanent and irreversible.
2025-03-04
Penelope
Which silicone is safe for making food molds or for skin contact?
Only platinum cure silicone is safe for food and skin contact applications, provided you purchase a grade specifically certified as "food-grade" or "skin-safe". The high-purity curing process ensures no harmful residues. Tin cure silicone contains a tin catalyst and releases byproducts, making it completely unsuitable for any application involving food or prolonged skin contact.
Only platinum cure silicone is safe for food and skin contact applications, provided you purchase a grade specifically certified as "food-grade" or "skin-safe". The high-purity curing process ensures no harmful residues. Tin cure silicone contains a tin catalyst and releases byproducts, making it completely unsuitable for any application involving food or prolonged skin contact.
2025-03-03
Lucas
Which silicone has lower shrinkage and why?
Platinum silicone has significantly lower shrinkage, often near zero (<0.1%). This is because its addition reaction directly combines Part A and Part B molecules with no material loss. In contrast, tin cure silicone's condensation reaction releases alcohol byproducts that evaporate, causing a loss of mass and volume, which results in higher shrinkage (typically 0.3% to 0.5% or more).
Platinum silicone has significantly lower shrinkage, often near zero (<0.1%). This is because its addition reaction directly combines Part A and Part B molecules with no material loss. In contrast, tin cure silicone's condensation reaction releases alcohol byproducts that evaporate, causing a loss of mass and volume, which results in higher shrinkage (typically 0.3% to 0.5% or more).
2025-03-02
Lana
What is the fundamental difference between platinum and tin cure silicones?
The core difference is their curing chemistry, which dictates their performance and applications. 1. Platinum Cure (Addition): Cures via an addition reaction with a platinum catalyst, producing no byproducts. This results in low shrinkage, high purity, and stability, making it suitable for food/skin contact. However, it is sensitive to cure inhibition from contaminants like sulfur and tin. 2. Tin Cure (Condensation): Cures via a condensation reaction with a tin catalyst, releasing alcohol as a byproduct. This causes higher shrinkage and makes it unsuitable for food/skin contact. Its main advantages are lower cost and resistance to cure inhibition.
The core difference is their curing chemistry, which dictates their performance and applications. 1. Platinum Cure (Addition): Cures via an addition reaction with a platinum catalyst, producing no byproducts. This results in low shrinkage, high purity, and stability, making it suitable for food/skin contact. However, it is sensitive to cure inhibition from contaminants like sulfur and tin. 2. Tin Cure (Condensation): Cures via a condensation reaction with a tin catalyst, releasing alcohol as a byproduct. This causes higher shrinkage and makes it unsuitable for food/skin contact. Its main advantages are lower cost and resistance to cure inhibition.
2025-03-02
Yvonne
What are the key physical properties of platinum silicone?
1. Hardness: Measured in Shore A durometer, it ranges from extremely soft gels (Shore 00) to very firm rubbers (Shore A 90), offering wide application versatility. 2. Temperature Resistance: Cured silicone performs well in a wide temperature range, typically from about -50°C to 250°C (-58°F to 482°F) or higher. 3. Color & Clarity: Many platinum silicones are available in translucent or even water-clear formulations, making them easy to pigment and allowing for visual inspection of casting inside a mold. 4. Chemical Resistance: It shows good resistance to many chemicals, UV light, and ozone, making it suitable for outdoor or long-term applications.
1. Hardness: Measured in Shore A durometer, it ranges from extremely soft gels (Shore 00) to very firm rubbers (Shore A 90), offering wide application versatility. 2. Temperature Resistance: Cured silicone performs well in a wide temperature range, typically from about -50°C to 250°C (-58°F to 482°F) or higher. 3. Color & Clarity: Many platinum silicones are available in translucent or even water-clear formulations, making them easy to pigment and allowing for visual inspection of casting inside a mold. 4. Chemical Resistance: It shows good resistance to many chemicals, UV light, and ozone, making it suitable for outdoor or long-term applications.