I will add my $0.02 for what it is worth. I started with Casting Crafts from Michaels, upgraded to Silmar 41, and then tried Alumilite. I am now debating which to buy next so perhaps writing this will help.
Castin Craft is $35 for 32 oz. You also have to purchase the catalyzer separately for $14. You can always find a 40% off one item for Michael's, but for arguments sake lets keep the cost at retail. So about $50 for 32 oz of resin. At 2oz per pen that is 16 blanks or a little more than $3 per blank. Pros: Readily available, no shipping costs. Sets up well without a need for a pressure pot. Smooth turning, polishes above average. Cons: Worst smell of the 3. Needed respirator for days in the garage after I was done.
Silmar 41 is $35 for 128 oz, catalyst included. However, this is considered hazardous flammable material and can only be shipped via ground. It cost me $31 to ship using Composite Envisions. So $66 for 128 oz, cost per blank is a little more than $1 per blank. Pros: Works great, plenty of time to work with material. Pressure pot is optional, I have done with and without. I prefer a pressure pot because small bubbles will appear as you sand if you are not careful mixing colors. This was the main reason why I went to alumilite. I figured if I needed a pot anyway why not try it. Cons: Smell is bad, but not as bad as Castin Craft. Still recommend respirator while working, but only while in direct contact. Cons: Sounds stupid, but I hate the can it comes in. I cannot pour out of it without making a disaster of a mess. I started pouring from a can to a secondary container before pouring into a third mixing cup just to reduce the mess. It also sucks to pay half the price in shipping. As far as I know only two online retailers sell it so it is difficult to obtain. You have to mix colors gently to avoid introducing air bubbles, or invest in a pressure pot to collapse those bubbles. I do not know about the other options, but Silmar has a short shelf life. They advertise a 3 month window. What I have stored in the can seems to be holding up fine, but I put some in a secondary bottle to use to fill molds and that thickened up significantly over time.
Alumilite is difficult to price. I tried the 2lb (32oz) kit direct from the manufacturer. The next size up from alumilite is the 16lb version. You can find the 8lb version from TurnTex, and other retailers sell it as well. Shipping is reasonable since it isnt considered flammable. For arguments sake I will use what I purchased as the example knowing if you buy in larger quantity it will cost less. No catalyzer is needed, it is mixed half and half. So 32oz cost $44 or $2.75 per blank. Pros: Easy turning. I can furn and sand a pen in half the time using this over Silmar41. That could also be a con if you are not careful. I tend to turn Alumilite a little fat and sand down to final size because it is easier and I have more control over the final result. Cons: Short working time, although not as bad as you would believe. I screwed up half of my blanks when I first tried it because I didnt have a plan going into it. Making alumilite blanks is different than making PR and I wasnt ready for that. I Purchased the clear slow version which advertises a 12 min working time. That is from initial mix of the two parts to in the pressure pot. By the time I got the hang of it I ran out of Alumilite. Pros: Smooth turning and sanding. Cuts working time in half when making pens. Only option of the 3 for worthless wood casting. I have not advanced to this level of turning and casting yet so I cannot provide input, but if you want to go that route then disregard the other choices and start here and never look back. Cons: Pressure pot required, no exceptions. So if you go this route understand there is additional costs in setup. Higher level of knowledge needed for Alumilite. You dont necessarily need to be smarter, but you need to plan your process out in advance and work well under time constraints. With Silmar 41 you have all the time in the world to get colors correct before you add the catalyzer and mix for 15 min. Alumilite is different. You can either mix both part A and B together then add color, or add color to one side then mix (diluting your color). I like to swirl 2 or even 3 colors together when casting, and I found Alumilite challenging to pull off. Granted, I have limited experience and I am sure those who use Alumilite regularly can provide better advice on doing this than I, but for my first time I was overwhelmed.
Hope this helps. As for me, I think I am going to go back to Silmar 41 for a while. I like the worthless wood castings and want to try it out, but I am not ready yet for the added expense involved with stabilizing wood. Silmar 41 is the best cost option despite the added shipping and I get great results almost every time.
