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This Alumilite casting resin is a great product with many possible uses and applications. We use it for casting parts for model trains, but the real limit on possible uses of this product is only your imagination.
It is a two part urethane resin, part A and part B come in two separate bottles. These are combined in equal parts, mixed and poured into molds. This type of urethane is used mostly with silicone molds, but other molds can be used as well. The most common products for making molds are Alumilite's Alumilite Quick-Set Mold Rubber Kit mold-making kit or Alumilite High Strength 3 RTV Mold Making Rubber 1 lb. HSIII RTV. Once parts A and B are combined, you have 90 seconds to mix and pour before the liquid starts hardening right before your eyes. The mixture heats up a bit but nothing that you can't hold in a plastic cup. The little heat is just a byproduct of a chemical reaction. In less then 5 minutes you can demold your casting and either paint or otherwise work it, i.e. machine it, polish it, cut it, etc.
The fact that you can machine it is really cool. We've done some machining on some of our castings and it can be worked very easily. It is soft enough and workable, yet firm and unbend-able. You can use some basic Dremel tools to work this stuff -no need for a heavy duty machine shop. On the other hand, if you have even a small machine shop, you can use this for creating prototypes of metal castings and machine it to whatever final shape you want. Think of custom auto parts for car restorations, for example. Instead of first creating an expensive mold and going through aluminum or iron/steel casting, you can create a prototype with Alumilite and machine it, send it to the client to check it and see if it meets their requirements.
When this particular version of urethane hardens, it's a yellowish or a bit darker tan color. Other versions of this base product are also available -Alumilite Rigid Urethane kit 28oz White by Alumilite Corp that hardens into pure white; and Alumilite Water Clear Casting Resin Kit 16 oz that hardens water clear. In addition, you can buy small bottles of tint or dye to create castings of just about any color. When the dyes are added to the urethane, it will harden to whatever color you add to it. We've done quite a bit of mixing of colors and had good results making our own colors (only about 6 or 7 basic/primary colors are available for purchase). And a very small drop of dye goes a long way. The dyes can be added to this or the white urethane with the same results, i.e. what type of urethane you use does not affect how the colors turn out.
When casting, it is best to preheat your molds before casting the urethane into them. While the urethane has a low viscosity and flows quite well, it's better to have a preheated mold. It simply flows and fills up better and you end up with a better casting. But either way, Alumilite will fill just about any crack and will perfectly fill your mold. Also, combining and mixing the urethane adds bubbles to which may create flaws in your castings. But this can be eliminated if you have a vacuum chamber and a vacuum pump and if not, you can minimize it by careful mixing and pouring. We've had very few issues with bubbles, which we mostly mitigated with careful mixing. If you have a vacuum chamber, be aware that the pot-life of this urethane is about 90 seconds. So once you pour part A into B you have 90 seconds to mix, de-air and pour. This is probably the only drawback of the urethane -I wish it was a bit longer but so far we haven't had any problems. There are urethanes on the market with longer pot life from other manufacturers, though they have longer cure and de-mold times. If this one does not fit you need you need to do some research and you'll most certainly find one that will.
In summary, this is a great product and if you like making molds and casting models or whatever you'll not only find this product very useful but also have a lot of fun working with it.
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