Alumalite Question

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andyk

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Can someone explain the difference between PR and Alumalite? Everything I see it seems that people are using the Alumalite to cast something embedded or bad wood blanks and PR for strictly resin blanks.
 
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I have no answers, but I do know people that use PR for casting worthless wood, so I know it does work for that. I notice a difference in turning the two materials. The PR polishes to a brighter shine easier, the alumilite seems a slight bit softer so it turns easier and doesn't dull the tools as fast. I think PR doesn't stick as well in worthless wood as alumilite, which may be because it is more brittle. If I'm wrong, any expert is welcome to correct me, these are just theories from me turning these materials which were cast from a large variety of people, and I have not gotten around to purchasing one or the other...have a pot for some time now, but I too don't know what I want to be using PR or Alumilite. Cash being the main hold back of course! I just keep reading so when I get up and do something, maybe I won't waste so much.
 
Alumilite is an urethane based resin and sets in 1 hour (max). You mix part A and part B in equal, 1:1 ratios in all weather, all temperature, all humidity.
PR is Polyester Resin and sets in several hours to overnight or longer (depending on mix). You mix your resin with a few drops of mekp catalyst and that mixture changes depending on temperature, humidity, speed of set you want, etc.

Alumilite is thin (some is "water thin"). PR is thick syrupy.

So, if you are doing something where the resin needs to penetrate deeply or you are trying to do "bulk" blank creation, Alumilite is your resin of choice. If you need long open times to do fancy swirls with ribbons and inclusions and blah blah blah, PR is a better choice.

PR is cheaper than Alumilite.

Other than those, really, it is a matter of preference. As Jeff said, there is some difference in "strength" of the blank and some difference in the finished blanks' ability to take a shine. But both of those are up for argument and both can be worked around.
 
pretty much what Greg says is correct, except that alumilite reacts to the the temp, weather and humidity.
if it is too humid it will cause the alumilite to foam. to cold it takes longer to cure. etc...
 
Obviously since I haven't cast anything in resin yet, I can't speak for the liquid form, but I do notice quite a difference in the smell between the two when cutting, drilling and turning as well. PR is quite smelly, I would think it smells alot stronger in liquid form. Is there a poll on which of the two people prefer the most for casting?
 
I have cast Alumilite when it was 92% humidity in my shop (based on a wall temp/hygrometer) and it did not foam at all. If the wood or item being cast is at all wet, even from high humidity, it will certainly foam.

Alumilite is actually harder based on the Shore D hardness testing that measures hardness of an object. Where it gets its different feel is in its elongation which is the amount a material will stretch before breaking. Alumilite has a lot more elongation than PR which is also what makes it less brittle when cured.

Alumilite also has virtually no smell and can be used without smelling up your shop when pouring or working with the finished blank. It can also be shipped with no hazmat fees, regardless of how large of a package you ship. PR requires a hazmat fee for larger quantities.

Alumilite costs about $80 per gallon. Not sure the cost of PR but it is certainly cheaper. Then again, PSI is cheaper than CSUSA!:)

Obviously I am a big cheerleader for Alumilite and have been using it since it first showed up on IAP. I would not consider any other resin but then again, there are folks that prefer PR.

Do you prefer Ford or Chevy? :) Same kind of question and will get the same type of responses!
 
PR Silmar 41 costs about $42 per gallon with shipping. VisExp(Keith Larrett) and I were just talking about the some of the differences with of PR to Alumilite or other Polyeurethane resins.

Polyeurethane resin is more scientific and methodological. You have X grams of A and X grams of B, mix thoroughly for X minutes- You have 30 many minutes till it is cured.

Polyester resins are more alchemical- we use three drops of excelerant, but because we added red dye we have 22 minutes to gel +/- the age of the resin and the excelerant, the local ambient temperature and oh yes we also added some white dye also so we add 50 minutes to the gel... it should be cured tomorrow sometime.
 
One problem is with shrinkage, Alumilite has almost no shrinkage (.005) while PR has a much higher shrinkage rate and will actually pull away from some objects that is cast with it. This is seen clearly when you cast in a solid mold and the PR pulls away from the sides and removes easily while the Alumilite will fill the area completly. The only problem I have had with humidity and Alumilite was when I had some sweat drip into the mix, otherwise, I just heat the objects in a toaster oven (dedicated) to remove any moisture that may have penetrated the surfaces.
 
How about another related question...penetration. PR doesn't seem like it penetrates into wood fibers very much, unless the wood is very pourous. Would Alumilite be a bigger risk, in that it will penetrate colors into fibers of a larger variety of woods where you don't want colors to be?
 
workinforwood said:
How about another related question...penetration. PR doesn't seem like it penetrates into wood fibers very much, unless the wood is very pourous. Would Alumilite be a bigger risk, in that it will penetrate colors into fibers of a larger variety of woods where you don't want colors to be?
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I don't think either one is going to penetrate to the point of stabilizing any wood. I have found that Alumilite will penetrate to a point, but then it hardens.
 
Right, not stabilize, but penetrate to the point that color in the alumilite might bleed lets just say 1/16 into the wood? I ask this because in many personal situations, I want the color in the hole, not in the wood at all.
 
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