Casting Woes

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Jmhoff10500

Jmhoff10500

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Joined
Nov 11, 2009
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Provo, Utah
So the snakeskins i have must have been from a snake that was owned by a magician because no matter how invisible they are before, bubble often form!

IMG_9903.jpg

This is the first skin that has done this in a while but it stumps me every time and it is a huge inconvenience cause i have to remove the resin and recast the skin...:mad:

So here is my procedure and if any of you guys know what is up, please let me know!!!

First i wrap the skins on painted tubes with CA and let them sit for almost 2 weeks to insure there is no more degassing. then from there i paint the tubes in raw CC PR, place in the resinsaver mold, slowly mix in PR Catalyst to insure no bubbles mix in, then slowly pour it into the mold, place on vibration table, let cure over night, post cure in homemade heat box, then pull them out of the mold.

The bubbles look too big to be degassing or preexisting bubbles in the resin, so im lost...

It seems like a shame to not use the ones with bubbles and a huge process to recast so if you guys have any ideas, please let me know!!! Thanks!
 
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I think you have a solid system there, Jonathan. If you're not getting these bubbles regularly, I wouldn't make changes. I think that sometimes we get bubbles. Nothing more to it than that. I don't think you need to recast though. I would turn that blank and fill with ca when I got to the air pockets. Eezy peezy and not uncommon at all.
 
Chris nailed it!

I was going to ask if you turned a bubble blank down to see if the bubble would be an issue or not. Sometimes they look alot deeper than they are, and sometimes you can get to it on the surface and fill it in with CA.

The only other thing i could think is that you wait an awful long time for the blanks to cure without introducing heat? I usually put my PR in the oven after about 45 minutes. They stay in the over for an hour or so (sometimes less, sometimes more) and then sit overnight.


I was having some issues with making "Prickly Pear skeleton" pen blanks. At first, i had massive amounts of air trapped, and i found a few things that helped tons.

First, I preheat the resin to 145. This gets it flowing much better than when room temp. I mix in the catalyst, and pour into a warm mold. In this case, you would want to warm the skins as well. When i pour, I use a back massager to vibrate the mold as i pour. This helps shake the air to the top.

Hope that helps!
 
Just curious, Have you tried to do it without "painting" the skin with resin first? Maybe it is a reaction between the catalyzed resin and the plain resin?
 
Air leaked out from under a scale and since it was on the bottom of the cast it stuck. I have seen this the main reason I don't like casting snake skins without pressure. But if you use pressure you can't use a resin saver mold.

Now some good news it can be fixed. If you PR and I think you said you did turn it to round even down to almost the skin don't hit the skin. Now pick at the air bubbles to open them up and just recast. The new PR will bond the the old with no problems at all. I saved many blanks like this. Thats the great thing about PR it will bond to it's self with no notable seams. Just as long as you don't put anything on it like wax then you would have to make sure it is clean turn it off and scuff it up.

Good luck
 
snyiper said:
I thought I had read somewhere to remove the scales to avoid this. Is this a viable solution?
Click to expand...

Yes and no I have done both methods scales on off it depends on the skin. If you take the scales off a dry skin some of the color would suffer. If the scales are loose and falling off a dry skin take them off easily done with an eraser. If the scales are tight I leave them on. The only advantage to taking the scales off is that you wont have a scale coming off wile casting and have a floating or dislodged scale ruin the cast. The problem with rattlesnake skin is the scale it self there is a hollow space under the skin of the scale not the sheded clear top coat. If you look at a rattlesnake skin it is not smooth the scales stick up like little pyramids they have like ridges down the middle that can hold air. Removing the clear top coat scale does not fix that problem. And then again it depends on the skin now take a python it is flat and smooth the scales are different.

So in my experience taking the scales off is only to prevent scales from floating. To avoid air problem and I believe that some of the air is leaking out of the inside of the scale it self. The only to stop this is to use pressure. Pressure will keep the air from leaching out of the skin. Now some will say coat it in CA and I do coat my money blanks in CA to keep air from leaching out. But I have not had much success with coating a snake skin with CA you can tell see the difference in the finished product.

Just some of my observations
 
I had that problem and found it was air escaping from the tube due to the heat. I just got me some syringes and either drill a very small hole and fill the void with thick ca or I make up a small batch of resin with hardner in it and inject it into the void. Sometimes I can just inject the solution into the end of the blank between the skin and the resin and fix it.
 
Stop post curing.
Do a good turn daily!
Don

Jmhoff10500 said:
So the snakeskins i have must have been from a snake that was owned by a magician because no matter how invisible they are before, bubble often form!

View attachment 33946

This is the first skin that has done this in a while but it stumps me every time and it is a huge inconvenience cause i have to remove the resin and recast the skin...:mad:

So here is my procedure and if any of you guys know what is up, please let me know!!!

First i wrap the skins on painted tubes with CA and let them sit for almost 2 weeks to insure there is no more degassing. then from there i paint the tubes in raw CC PR, place in the resinsaver mold, slowly mix in PR Catalyst to insure no bubbles mix in, then slowly pour it into the mold, place on vibration table, let cure over night, post cure in homemade heat box, then pull them out of the mold.

The bubbles look too big to be degassing or preexisting bubbles in the resin, so im lost...

It seems like a shame to not use the ones with bubbles and a huge process to recast so if you guys have any ideas, please let me know!!! Thanks!
Click to expand...
 
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