When you think of making detailed, accurate and durable molds, silicone rubber becomes the ideal mold making material. Following are some of the fundamentals of silicone mold making that apply across industries.
Silicone rubber has emerged as the go-to material for most mold making projects on account of its excellent properties like flexibility, durability and ability to capture intricate details. Understanding the basics about this material will go a long way in helping to make a professional silicone mold with ease and confidence.
Choose the right silicone – There are two major types of RTV silicone – addition cure and condensation cure. Mold makers have to proceed with caution as these two are very different from each other in both properties and applications.
Addition cure silicone rubbers use platinum as the catalyst; the molds provide excellent detail reproduction with good dimensional stability and are ideal for intricate molds or those with undercuts.They are preferred for precision molding, special effects applications, encapsulations and paints.The curing is not affected by humidity; theyoffer exceptional heat resistance and work better in high temperatures. However, presence of sulfur can inhibit the curing.
On the other hand, tin is the catalyst in condensation cure silicones. These molds offer good tear strength and are suitable for general mold making applications including prototype applications and prosthetic works. Keep in mind that they require moisture for proper curing; excess humidity or even application of heat can speed up the cure time. Some shrinkage is to be expected.
Mixing and Pouring–The silicone and catalyst have to be measured as per the manufacturer’s instructions and mixed together properly for best results. Precise measurements are especially essential for platinum cured silicones. The liquid rubber must be poured carefully into the mold box that contains the master. The curing time will also be specified by the manufacturer.
Degassing – All silicone rubbers have a natural propensity to capture air no matter how carefully they are mixed or poured. The result is ugly bubbles marring the surface of the mold. Therefore, the rubber should first be degassed in a vacuum chamber with pump to remove the trapped air.
Finishing – Silicone rubber does not stick to anything but itself. Therefore, using a release agent is not mandatory. However, many mold makers prefer to apply a release agent to ensure that the master is not harmed and the mold can be demolded with ease. Excess silicone on the mold can be trimmed with a scalpel or craft knife.
Storage – Silicone molds should be cleaned and dried properly before storing in a drawer. Applying some talcum powder will ensure that it does not turn sticky. Properly stored silicone molds can last for years.
Finally, when it comes to sourcing, the best resource is the manufacturer and supplier EnvironMolds (https://www.artmolds.com/). The website offers a broad range of mold making and casting silicone rubbers - including food safe, skin safe and transparent versions – apart from other materials, tools, supplies and equipment.
Silicone rubber has emerged as the go-to material for most mold making projects on account of its excellent properties like flexibility, durability and ability to capture intricate details. Understanding the basics about this material will go a long way in helping to make a professional silicone mold with ease and confidence.
Choose the right silicone – There are two major types of RTV silicone – addition cure and condensation cure. Mold makers have to proceed with caution as these two are very different from each other in both properties and applications.
Addition cure silicone rubbers use platinum as the catalyst; the molds provide excellent detail reproduction with good dimensional stability and are ideal for intricate molds or those with undercuts.They are preferred for precision molding, special effects applications, encapsulations and paints.The curing is not affected by humidity; theyoffer exceptional heat resistance and work better in high temperatures. However, presence of sulfur can inhibit the curing.
On the other hand, tin is the catalyst in condensation cure silicones. These molds offer good tear strength and are suitable for general mold making applications including prototype applications and prosthetic works. Keep in mind that they require moisture for proper curing; excess humidity or even application of heat can speed up the cure time. Some shrinkage is to be expected.
Mixing and Pouring–The silicone and catalyst have to be measured as per the manufacturer’s instructions and mixed together properly for best results. Precise measurements are especially essential for platinum cured silicones. The liquid rubber must be poured carefully into the mold box that contains the master. The curing time will also be specified by the manufacturer.
Degassing – All silicone rubbers have a natural propensity to capture air no matter how carefully they are mixed or poured. The result is ugly bubbles marring the surface of the mold. Therefore, the rubber should first be degassed in a vacuum chamber with pump to remove the trapped air.
Finishing – Silicone rubber does not stick to anything but itself. Therefore, using a release agent is not mandatory. However, many mold makers prefer to apply a release agent to ensure that the master is not harmed and the mold can be demolded with ease. Excess silicone on the mold can be trimmed with a scalpel or craft knife.
Storage – Silicone molds should be cleaned and dried properly before storing in a drawer. Applying some talcum powder will ensure that it does not turn sticky. Properly stored silicone molds can last for years.
Finally, when it comes to sourcing, the best resource is the manufacturer and supplier EnvironMolds (https://www.artmolds.com/). The website offers a broad range of mold making and casting silicone rubbers - including food safe, skin safe and transparent versions – apart from other materials, tools, supplies and equipment.