White Spots in my Alumilite Clear

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keithbyrd

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I painted this musk ox horn blanks with Alumilite clear. What caused the white spots? I have done this several times before with no problem. Will it clear up?
 

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JohnU said:
I believe that is from moisture. Could be in the horn or the air. Warming the horn and pressure tank prior to casting should help.
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Thanks John - I should have been more specific - I didn't cast it - I painted it and put it in a toaster oven for 30 minutes at about 130 degrees. trying to warm and cure the alumilite. These are old horn - haven't had the problem before.
 
Alumilite is doesn't like moisture. Looks like the oven pulled some minuscule moisture out of the horn and it reacted. Was this particular horn allowed to sit in a humid environment or ambient outside air or unheated room before you used it?
 
Just to add my 2 cents. It could be the ratio was off a bit. Alumilite will turn milky if not measured and mixed correctly. Why use an oven? As mentioned before it could be moisture and when the resin starts to set and cure it gets hot. That could cause moisture and air to cause problems. When you put it in an oven that would just add to the possibility of problems. I'd put the horn in the oven first to dry it out and warm it up so maybe the resin will flow easier into the cracks and crevices. Put it in the oven at the temperature you mentioned for about 30 minutes. Then mix your resin and pull out the horn and paint on the resin. Then just let it set. I am surprised the urethane resin worked before without issues. I'd try an epoxy resin for that process. IMHO. Good Luck.
 
Kenny Durrant said:
Just to add my 2 cents. It could be the ratio was off a bit. Alumilite will turn milky if not measured and mixed correctly. Why use an oven? As mentioned before it could be moisture and when the resin starts to set and cure it gets hot. That could cause moisture and air to cause problems. When you put it in an oven that would just add to the possibility of problems. I'd put the horn in the oven first to dry it out and warm it up so maybe the resin will flow easier into the cracks and crevices. Put it in the oven at the temperature you mentioned for about 30 minutes. Then mix your resin and pull out the horn and paint on the resin. Then just let it set. I am surprised the urethane resin worked before without issues. I'd try an epoxy resin for that process. IMHO. Good Luck.
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Thanks Kenny - did it backwards - painted then heated. I think its going to work though. I have one in the pot now to see how it will come out. if not that is an expensive lesson - 12 Musk ox horn blanks!
 
leehljp said:
Alumilite is doesn't like moisture. Looks like the oven pulled some minuscule moisture out of the horn and it reacted. Was this particular horn allowed to sit in a humid environment or ambient outside air or unheated room before you used it?
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No it was in my shop - its about 6-7 years old so its dry but heating it first may have caused a bit of a problem!
 
keithbyrd said:
No it was in my shop - its about 6-7 years old so its dry but heating it first may have caused a bit of a problem!
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Dry is not necessarily dry enough. The moisture content needs to be as close to 0% as you can get it. That's why most people recommend cooking the wood at low temp until its thoroughly dry. I then put it in a sealed ziplock bag, suck the air out with a straw and leave it until it cools and I am ready to cast it (usually an hour or so). That way it doesn't draw any ambient moisture back in.
 
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