# Anyone know what causes?



## Az Turnings (Jul 24, 2018)

a friend just casted 5 pen blanks and every one had this same issue? Any help would be greatly appreciated!


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## rocky1 (Jul 24, 2018)

I'm assuming it was supposed to be black and white, and you're looking at the bubbles? 

What kind of resin was he using Blake?

Moisture in the blank could be the culprit, especially with alumilite. Urethane resins don't like moisture; poly doesn't like a lot of moisture, but it is a little more forgiving. 

If you're using alumilite, it creates bubbles as it cures, hence the need to cure it under pressure. Hence the need to stabilize before pouring, because if you don't, it forces air out of the blank under pressure, causing more bubbles than it normally creates. Dependent upon material used in the blank it could be air trapped in the blank, or a reaction to the alumilite. 

If it changed color, and bubbled up, the first question would be... Is he using Poly Resin by chance? 

Poly doesn't create bubbles in the curing processing. Putting it under pressure on an unstabilized blank can and will force air out of the blank as it pushes resin in however. If it does so right away, it's not a bad deal, it works out and goes away. If it does it later in the curing stage, as resin has cured away from the tube and bubbles can't move so freely, then it will often stick to the blank, as a result of resistance in the resin and surface tension on the blank itself. 

If it was only on the bottom of the tube, the bubbles stuck to the tube and didn't move, suggesting he poured the mold to quickly. Pour slowly and fill from one end so it works the air out ahead of the rising resin. Tip your mold slightly while you pour, leveling it as the resin rises around the tube and the mold fills. Kinda like pouring keg beer. Vibration would likely cause them to work around the tube and go away also. Run the blade below surface on your saw and sit the blank on top with it running. 

My research on resin changing colors has indicated poly resin doesn't always play well with urethane dyes. Sometimes works, sometimes doesn't, really confuses everyone that it happens too. It really isn't talked about a lot on the internet either. In fact I didn't find in a wood working forum, I found more info on that topic on Craft/Hobby site. 

What I've discovered in my personal experience is there are some truly weird things go on it that scenario. Had 2 blanks in the mold together poured one color on one end of the mold, and a second color on the other end of the mold, in the same mold, poured at the same time, mixed at the same time in the same manner, using the same resin and catalyst, only thing different was the dye... One end turned a color I didn't pour, the other end turned a dark metallic gray. 

However, it was poured when it was cool in the shop, and my resin didn't set like it was supposed to. The end that turned gray, went from Blue, to Purple, then to Gray. And, only set after I put a heat lamp on it and warmed it. The end I poured in red changed color, but didn't go to that extreme. 

I tried another pour, again under cooler conditions, increased my catalyst, and while it did change color a little, it wasn't as bad. Next little pour I tried, I effectively doubled the amount of catalyst called for, it was in fact trying to kick as I poured it, threw it in the pot quick, got pressure on it, and it appears to have worked perfectly. Except it set in my cup before I could the mold in the pot, lid on, tightened down, and get back to wipe the cup out. 

And, I've seen the same problems with color change on poly using both liquid and powdered dyes, colored pearl, inks, you name it! 

So temperature and dye both have a profound effect on color change. The longer the resin takes to set, the more drastic the change in color, on dyes that are more susceptible to change.


So at least one individual suggested Alcohol based inks are supposed to play better with poly. And, I invested $35 - $40 in alcohol based inks to try that. Mixed my resin, added ink, poured 2 blanks, each did something a little differently, because they all look cool sitting on the bench under the light, but they all turn a different color when you hold them up, and when you hold them directly under the light, they definitely change color! 



 




 



 


If I've learned anything playing with Resin, it's that I don't know anything!!

Reactions: Way Cool 1 | Informative 2


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## Az Turnings (Jul 24, 2018)

Thanks for the response @rocky1 we are thinking maybe moisture got in the sticker? We’ve had 50-80% humidity. I’m not sure on what the stamp is but it’s a stick on so maybe the heat of the alumilite pushed the sticky goo out of the seam of the stamp?

Reactions: Like 1


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## Az Turnings (Jul 24, 2018)

It is alumilite

Reactions: Like 1


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## rocky1 (Jul 24, 2018)

@Schroedc - If it's a sticker or a stamp glued to a tube, Colin is your go to expert there. 

It honestly looks like a moisture problem Blake. But it could be a reaction to adhesive on the stamp. Colin was using Silmar 41 when casting his stamp blanks. I think he said it played better with the inks on the stamps, and it is much cheaper. As best I recall, he was washing the adhesive off, and then gluing them on the tube with Hodge Podge Craft Glue. 

The Busy Bee blanks I poured with the hair ribbon wrapped on the tube, he suggested the Hodge Podge glue, and there the only problems I had were with the occasional bubble sticking under the tube on the ribbon. Colin also suggested the vibration routine on the table saw, and cured most of that problem, coupled with pouring slowly from one end with the mold slightly tipped I pretty much eliminated it altogether. 

Bubbles on these bottle stoppers are as I learned after the fact, indicative of moisture in the blank when cast. Hence the reason for everyone adding pearl, this stuff just kinda fades right into that. 



 





Personally, I like the effect, I don't know why anyone would want to cover it up. The matching bottle opener that I poured with these stoppers is cooler yet, but the wife grabbed it and disappeared with it before I got pictures. But, I guess if you get too much moisture it just gets cloudy, rather than get the cool smoke in the valley appearance seen in the deep surface, top stopper in the second picture. The bottle opener has that effect going on the length of the blank, and just really looks cool. 

Wooden blanks they recommend heating in the oven for 24 hours ahead of casting to dry them, not supposed to let them cool all the way either, or they start reabssorbing moisture. On a stamp wrapped tube, I would think a few minutes with the blow dryer would probably dry that out. I honestly can't imagine it holding enough moisture to cause that much of a problem, but maybe. 

If you're using alumilite, I presume you're casting this under pressure?? My experience with alumilite is, it really doesn't perform well without pressure. Silmar 41 works a whole lot better without a pressure pot if you don't have one. You will get a few bubbles occasionally, but nothing like alumilite.

Reactions: Informative 1


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## Schroedc (Jul 25, 2018)

Was the tube undeneath painted black? Was the sticker sealed with CA for something?


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## Schroedc (Jul 25, 2018)

Sticker adhesives occasionally don't like resin and come loose. Also if the tube was painted instead of powder coated the paint may have listed. I use powder coated tubes. In the classroom area I think is my tutorial on stamp casting, my be info you can use there maybe @ripjack13 can find it and post a link as I'm in the stupid phone right now.

Reactions: Like 2


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## ripjack13 (Jul 25, 2018)

https://woodbarter.com/threads/casting-vintage-stamps-in-acrylic-using-silmar-41.28858/

Reactions: Thank You! 2 | +Karma 1


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## TimR (Jul 26, 2018)

Agreed on casting under pressure with Alumilite, but also can help to remove entrained bubbles in both A and B using vacuum pump prior to mixing. Pressure helps shrink the bubbles, but if they aren’t there to start (or minimized), better still.


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