Alumilite problems?

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NewLondon88

NewLondon88

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Wondering if anyone had these problems or knew of ways to solve them

Just tried (about 10 times) to pour a black base for pen holder,clock etc.
about 10x6x1" . I made a silicone mold, mixed the crystal clear with the black
dye and poured.

I find the top surface turns whitish/gray toward the center. This isn't so bad,
since the top is really the bottom, and the white/gray color is always at
the top of the cure. But I wonder what it is.

Also, the casting is full of bubbles and blisters. I mean . .some of the
blisters raise up out of the surface 1/8" or more. Large blisters might be
2-3" across. Pinholes don't seem to clear, even with vibration.

I've sanded down the blisters and poured again, but they keep coming
back and that white/gray color is always there. I've changed mixing cups
to different plastic types, thinking there may be some sort of reaction
with the materials. I've noticed that when mixing the clear alone, this
whitish color can show up in clear casts, too.

Any ideas? I've been through about 3/4 of a two gallon kit trying
to make this base..
 
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I don't know. I always end up with some blisters when I pour a large mold, but they are really tiny and just show up in a few small areas. The top of the pour..colored of course, always looks like several large imperfect circles and it's the intersection of multiple circles where the micro blisters appear, but they are not through the block, just on the surface. It looks like when it is poured...and as it cures, it must boil...not a rapid boil like water on a fire, but you know what I mean..because when cured you get those boiled looking circles. I have no white film on top. I do not know the answer. It seems to me near impossible to get a large mold like that to come out completely flawless on the very top surface, but you can sand it down and polish it back up.
 
Haven't got a clue about the Alumilite Charlie but maybe for this instance you could pour PR ( or get the Princess to do it. ) Alternately, if you're running out of time, then perhaps a piece of black corian? Maybe even the flavour with little sparkles in it?:wink:
 
I've also tried the PR, also with lots of pinholes. Might not be a problem if I
had a large enough pressure pot, but I don't.

Also tried sanding, buffing and that didn't work. Sanding takes off the blister, but it
takes it down to below the rest of the surface, so instead of a blister, I get a crater.
I'm going broke on this one!

I also made the mold from Corian. Mold came out fine.. but I can't find black
anywhere. I also hate the look of Corian.. but it's good for cutting, polishing and
making positives..

The white isn't so much a film as a coloration.. almost as if the plastic cup has
started to melt and the color of the plastic is introduced into the resin. Don't know
that for sure, just my impression so far. That also happens in clear casts, depending
on the type of plastic cup I mix in
 
I know nothing of alumalite's properties, but it sounds like some sort of contamination issue. Similar to fisheyes in auto paint if there are silicones present.
 
NewLondon88 said:
I've also tried the PR, also with lots of pinholes. Might not be a problem if I
had a large enough pressure pot, but I don't.
Click to expand...

Mmmmm, could you perhaps lay it on it's side? ( the pot, not the mold )I got a large rectangular baking tin in mine like that:wink:
 
You beat me to it Steve..I was going to say the same thing. I didn't realize you weren't using a pot! If the silicone mold is a bit flexy, just put a piece of plywood under it so it doesn't sag into the curve of the side of the pot. It would really help if you could get an assistant to help you with the lid in that situation.
 
Switch to Alumilite RC3 Black. It is a different formula and already has the black color in it. It is also cheaper. There is no point whatsoever in using a clear, more expensive resin just to turn it solid black. It also works better than the CC without pressure.
 
Charlie, I have been having some issues as of recently and have decided that it is due to the humidity around here with all this rain. I have 2 large dehumidifiers set up and am working with those trying to stop the problem. If you have the time, wait until we get a couple of dry days and the air dries out a little.
 
From what I know so far...

Pressure pot: the biggest problem would be getting everything level. Since the
positive I cut from corian is chamfered, I was hoping to get something close to
finished coming right out of the mold. So far the surface has been terrible ,unless
I pour about 1/8th of an inch at a time. Then the surface looks ok ,but the back
doesn't ..

Humidity: The whitish part also happens when dry, this is the first time I've
tried anything this large, so it is more noticeable.
I suppose I have the time to wait .. she doesn't know about the pen yet.
But I'm anxious to get this done.
I used to pour synthetic marble trophy bases all the time .. even in 100%
humidity, so I didn't really think about it. Perhaps these resins are more
susceptible to moisture problems?

"no point whatsoever in using a clear, more expensive resin" ..

4 points ,actually.

1) I already had it and
2) it's paid for.
3) Plus, I had no way of knowing ahead of time that it wouldn't work.
4) and I can't afford to keep going out to buy more product if I
think that what I already have will work.

Type of silicone: this is tin cure. The platinum cure is just not in my budget
right now. I've done it with and without release, but this doesn't seem to change
anything except that the release leaves it's own impression in the casting. I know
that the Silmar can have issues with tin cured silicone, so I wash the mold with
denatured alcohol first , as recommended by US Composites. I was trying not to
use PR because of the shrinkage. Sort of defeats the purpose of using a mold..

Thanks for the brainstorming, guys..
 
It will work, my point was just that if you are going to be doing this a lot, you might want to use a different resin that is already black to begin with. Your best bet would be to give Mike at Alumilite a call and ask his opinion. He knows a lot about casting just this sort of thing. I know a lot about Alumilite for use in pen blanks but like most of us trying to answer you question, have never used it in large sizes such as you are doing.
 
Charlie, have you taken one of them with the grey surface and sanded it down to the black again? If you do that, you should be able to polish it back to a high shine and fill any pin holes with CA.
 
This is with crystal clear .. and as for sanding it back, it sands back to craters when
the blisters are sanded off. Probably 1/8" deep or so. Filling pinholes with CA ..there's
probably a couple hundred.
The whitish stuff is happening with clear casts, too. Looks like someone put drops of
milk in the resin. That's even using the little 1 oz cups supplied by Alumilite, so maybe
it isn't the plastic after all.
I hope this doesn't mean use something else from March to October.. cause I can't
afford to move to TX .. :tongue:

Might need to do this with an onyx resin, but I can't any prices online.
Hell, can't even find much in the way of info on it. I've got mfg. #'s
but can't find anyone local to talk to. I don't mind doing things online
but I'd rather speak to someone face to face first.. let them see what
I need firsthand .. then I can deal online after that.
 
I hope this doesn't mean use something else from March to October.. cause I can't
afford to move to TX .. :tongue:
I can assure you one thing.............as it stands now with the heat, curing time......27 seconds........in the shade!:umbrella:
 
Charlie , I made a couple of plaques out of the General purpose resin that HD sells . they were about 10" x 10" x 1/2" and they came out fine . I colored the resin with black powdercoat powder , it was a real pain to get the powder to mix well but finally got it to work . The GP resin costs about $35 for a gallon and works well for colored casts but it turns to powder instead of shavings when you turn it .

The white stuff may be moisture that is getting into the mix while you are mixing or while it is curing . With all the rain we have had lately I can't even do an alumilite cast right now , it's way too humid in my shop , the stuff just foams up .
 
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I can vouch for those issues too. Pouring is a challenge right now. The stuff can turn to jelly before it leaves the cup, and it is a bit foamy on top, but if you pour a bit extra, cut off the top and the rest is fine.
 
Charlie, CALL MIKE AT ALUMILITE!!!

Other than that, the white you are mentioning is not normal. I did some pure resin blocks with no colorant when I was testing this stuff and it turned out completely clear with no blushing. Maybe it is your mold?
 
I'll call Mike as soon as I have some free time during business hours. He's on my
(ever growing) list.
I've also had clear casts with no color or blushing, but not lately. and this includes
just sitting in the mixing cup.

FWIW, what I'm seeing doesn't look like foaming, even under a 30x microscope, but
it is possible that it is very fine bubbles, I guess.

The HD resin might be an option.. is it different than the normal PR? I've still got a
few gallons of that but the shrinkage makes it tough to mold.. I suppose I could just
use the mold to get the rough size and then machine it from there.
 
I vote on totally black corian! You say you don't like the look but Corian,but Corian IS Acyrlic!!!! Especially the coal black. With a router and some sanding you would have a base in just a few minutes! Alice

Yes, Black is difficult to find, probably because scuffs show easy as they would any solid dark color and isn't picked as often for a counter tops, making "scraps" harder to find.
 
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I've been trying to find black Corian here for years, but nobody has it or wants it.
Everything looks like that flecked kitchen countertop stuff.

By the way .. I used a chunk of gray and a router/shaper and made a base, but I
used it to make the mold so I could make a black one.
I had a base in minutes, just not one I'd want anyone to see.

I did use the general purpose Bondo resin to make the base in the pics (other thread)
and it worked out fine except as mentioned, the color wasn't so easy to mix in.
I didn't have liquid dye so I used a powder from Douglass & Sturgis. Iron oxide, I
think.
 
Charlie
I have a gallon of Alumilite RC 3 black & would be more than happy to ship you a pint or quart. I'll be in West Hartford, CT on Friday and can send it from there or send it on Tuesday from here in Va if your interested. Curtis recomended it to me last February and I'm very satisfied with the results.

Let me know if your interested
 
That base looks great!
I guess I have been fortunate to be able to find solid black.
 
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Getting ready for my third try. I am going to insert a labeled tube inside the bullet, heat it, pour the Alluite into it, put it into the mold and flood it with the rest of the Allimilte, stick it into the painters pot 60 lbs, 45 min, and then bake at 150 for 30 more minutes.
 

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