Of all the mold making materials, I most often use silicone rubber for my molding and casting projects.
That is because silicone rubber is a very versatile material, as it can be used to reproduce almost anything. The molds replicate without the loss of the detail of the original, as silicone rubbers captures the minutest of detail, even down to the finger prints.
One can chose a very soft rubber to aid in demolding stacking blocks of undercuts, or a more firm silicone which will provide many more castings without losing detail. Apart from being easy and safe to use, silicone rubber molds have a fairly long library life. You can continue to use the same mold or molds for reproductions again and again which often offsets the higher cost of silicone rubber.
What’s more, the same silicone rubber compound can be used for mold making and as well as casting. Indeed, the same silicone can be used for making castings as easily as for molds. However, the downside is that silicone does not stick to anything apart from itself. Thus, a good mold release must be carefully used. So I prefer not to make silicone molds and castings of the same object.
Of all the variety of silicone mold rubbers available on the market, my particular favorite is a two-part putty-like silicone material that sets in only five minutes. The fast curing product stands up to its name as I can make a traditional silicone mold very quickly and easily, that too without using a mold box. I use it often for making quick impressions and also for food molds as it complies with FDA standards.
The material comes in two parts, each part about the thickness of standard putty. To use cut equal parts of Part A and Part B and combine them, mixing them in your palm. Each part is a different color so once the colors are fully blended without any marbling the silicone has been properly combined. Simply place the putty around the original piece. It’s set in five minutes. It is thick enough when cured, that I often do not need a mother mold or a mold box, another benefit of this product