Snake skin casting problems

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RONB

RONB

Passed Away Jan 17, 2011
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Joined
Jun 19, 2007
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Location
Marrero, La., USA.
I have been casting some snake skins and have a problem. Using P.R. with 3 drops of hardned per oz. Pouring into a mold that is 1"x1"x3". Corks in the tube ends. BB's inside for the weight. Shop is 70 degrees, humidity is at 50%. Pressure pot used at 25 p.s.i. for 24 hrs.
My problem is that there is a sheen,or what looks like an air pocket that develops along the side of the skin under the p.r. It varies from just a little spot to almost the entire blank. I've run out of ideas and am asking for help. Has anyone hade a similar problem? If so what was the fix?
 
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Go to the search feature here and type in casting snakeskin blanks and you will see alot of responses to this. I do not do them so can not help.
 
Man...I know the answer but it escapes me. This is a very common problem. I think it has something to do with sealing the skin. The thin film is air that was under the scales. Do some testing..spray a skin that is on a tube with polyurethane. Let it cure for 2 days and then cast that. I think it will work...gotta think positive!
 
I had that problem when I used skins that were not completely dry from oils. I let mine sit for a month with the back salted to dry the oils out, replacing the salt every week. (after wiping the outter surface with water and dishsoap to remove the oils they were shipped to me rubbed down with.) I also set the molds with the glued tubes of skin in the heated oven to get them warm before I pour the PR. When I take the blanks out and cut them apart, it looks like an air pocket along the skin in the block form but after I turn them down, it disappears. I guess it has to do with reflection in the square shape???
 
rjwolfe3 said:
PM PRPrincess or its_virgil. They are both masters at casting skins.
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Just so you know Dawn is not "Withholding information". We get that problem on some of the skins she casts, too.

One of the reasons the snake-skin blanks cost as much as they do is the "failure-rate". The condition you describe happens - we don't know how to stop it, entirely.

So, we watch these threads for ideas, then try various approaches, resulting in either more or fewer failures.

This ain't no science, wethinks!!!
 
The material they tan the skins is usually glycerine and isoproply alcohol. Having seen a number of these skins, it is likely that the mixture is not always the same concentration and that there is residual glycerine on surface of the skins. I actually did some chemical analysis of the surface and found glycerine. The significance of this is that too high a concentration of glycerine does not allow the resin to wet the surface - similar to water beading up on a newly waxed surface. The 2 known solutions to this are to clean the skins with isopropyl alchohol to remove some of the excess glycerine or "paint" the skins with uncatalyzed PR and make sure it does flow on the entire surface prior to casting. It will get plenty of cure when the catalyst from the main pour is nearby.

If you look at the cross section of the areas under a microscope you will see a void there. Note that these type of voids cannot be eliminated by using a pressure pot and increasing the pressure. The pressure pot only works to keep dissolved gas in solution. It will never shrink a void as some think.

And ED - this is SCIENCE!!!
 
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Not knowing a thing about casting skins, I submit a suggestion in the form of a question: Would pulling a vacuum before applying pressure help remove the trapped air?
 
pianomanpj said:
Not knowing a thing about casting skins, I submit a suggestion in the form of a question: Would pulling a vacuum before applying pressure help remove the trapped air?
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Pulling a vacuum on the resin prior to casting does release some of the air in solution, although many prefer using ultrasonics as a cleaner method to do this. Vacuum will do nothing for the void described in the original post.
 
Hey Bruce, IF Dawn had you in the lab (kitchen to the rest of us), the system COULD BE science.

Right now it's SOTP (Seat of the pants)!!!


Stop by any time, we'll move enough junk that you can sit on one of the stools!!!
 
Sounds like Ed's Kitchen Lab has a vinegar/oil mixing issue with the PR. Or perhaps better described as a surface tension/wetting agent process. Pressure and vacuum will not materially address either situation. Anyone tried Shellac as the sealer and intermediate layer that allows the skin and pr to work together?? I have used shellac to seal knots and silicone oils from other finishes. It should not react with glycerine.
 
ed4copies said:
Hey Bruce, IF Dawn had you in the lab (kitchen to the rest of us), the system COULD BE science.

Right now it's SOTP (Seat of the pants)!!!


Stop by any time, we'll move enough junk that you can sit on one of the stools!!!
Click to expand...
I'm on the way - put more water in the soup.
 
I'll second the shellac idea, because shellac is amazing in what it can do. shellac will cover over silicone, where any other finish would bead up. Shellac can go under or over any finish with no issues. I don't like shellac as a final finish, but I think with it's properties, it is a perfect candidate for experimenting on skins.
 
I wish I could say I've not had that problem, but I can't. Well, I could and make myself sound really great but it would be a lie and quite deceptive. I actually have a large box full of this type on failures along with others you will encounter if you continue. I can only offer some advice.
(1) Clean the skins and try to remove as much of the tanning chemicals as you can, especially the glycerin...as Bruce has mentioned.
(2) I no longer use BBs but pack the tubes with play-dough. Cork one end, pack in the clay and then the other cork. I no longer glue in the corks and have seldom a leak. If so, it stopes at the clay instead of surrounding the BBs. Thanks to Roy, aka Oklahoman for sharing this tip a bout the clay.
(3) I have coated the skins with fingernail polish (clear of course :biggrin:), lacquer, and other stuff I suppose. Thanks again to Roy, I now use CA to coat the skins. I let them set a day or so to totally dry and outgas before casting.
(4) I also do as Bruce suggested and paint uncatalyzed PR onto the skins as I place them in the mold.
(5) I now use an ultrasonic cleaner to help get rid of air in the resin. I love it and will not go back to the vacuum pump.
Has this totally solved the problem you are seeking to solve? No, but it has decreased the frequency and makes me much happier. One more tip. Be sure the blanks are nice and hard before removing them from the mold. Any bending of softer cured castings while removing them will cause the PR to separate from the skin and this problem will happen...even develop hours later. I know, sounds absurd but it happens to me. I leave the blanks in the pressure tank several hours, or at least leave them in the mold for several hours. I hope the tips in this thread improves your casting of snake skins. You've gotten some good advice from several who know of what they speak.
Do a good turn daily!
Don



RONB said:
I have been casting some snake skins and have a problem. My problem is that there is a sheen,or what looks like an air pocket that develops along the side of the skin under the p.r. It varies from just a little spot to almost the entire blank. I've run out of ideas and am asking for help. Has anyone hade a similar problem? If so what was the fix?
Click to expand...
 
We who cast snake skins all have our "bucket of rejects". I've cut way down on these over the last year by what Don said. Clay packed tubes, ultrasonic, coating of the skins with everthing from lacquer to finally CA which seemed to work the best, now I've tried coating with PR that hasn't had the catalist added which so far has proven effective and saved me from having to wait for the CA to off gas. I heat the PR to 125 degrees to thin it before applying. I've only tried this on the last 3 castings all came out good, so its still in the trial stages. Hope this helps.
 
Roy, remember when we talked several months ago? I was coating the skins with uncatalyzed CA prior to casting and letting them set for 10-15 minutes to make sure the PR soaked into the scales and under them. I was having great success that way then it started again...the silvery coating on the skins. After we talked I started doing CA and was getting excellent results again then...you guessed it. That silvery business started creeping back. Several perfect castings either way, then WHAM!! that little grimlin stricks again. For me it is unpredicitble even when I do things exactly the same way. :mad: But, I can almost guarantee it will happen when I don't need it to happen. But, thankfully, the bad castings are getting fewer and fewer but I hate it when it happens. Lots of time consuming work down the tubes.

I also heat the resin. My ultrasonic cleaner has a heater and I put in hot tap water.

Do a good turn daily!
Don

OKLAHOMAN said:
We who cast snake skins all have our "bucket of rejects". I've cut way down on these over the last year by what Don said. Clay packed tubes, ultrasonic, coating of the skins with everthing from lacquer to finally CA which seemed to work the best, now I've tried coating with PR that hasn't had the catalist added which so far has proven effective and saved me from having to wait for the CA to off gas. I heat the PR to 125 degrees to thin it before applying. I've only tried this on the last 3 castings all came out good, so its still in the trial stages. Hope this helps.
Click to expand...
 
it w

OKLAHOMAN said:
We who cast snake skins all have our "bucket of rejects". I've cut way down on these over the last year by what Don said. Clay packed tubes, ultrasonic, coating of the skins with everything from lacquer to finally CA which seemed to work the best, now I've tried coating with PR that hasn't had the catalyst added which so far has proven effective and saved me from having to wait for the CA to off gas. I heat the PR to 125 degrees to thin it before applying. I've only tried this on the last 3 castings all came out good, so its still in the trial stages. Hope this helps.
Click to expand...

its_virgil said:
Roy, remember when we talked several months ago? I was coating the skins with uncatalyzed CA prior to casting and letting them set for 10-15 minutes to make sure the PR soaked into the scales and under them. I was having great success that way then it started again...the silvery coating on the skins. After we talked I started doing CA and was getting excellent results again then...you guessed it. That silvery business started creeping back. Several perfect castings either way, then WHAM!! that little grimlin stricks again. For me it is unpredicitble even when I do things exactly the same way. :mad: But, I can almost guarantee it will happen when I don't need it to happen. But, thankfully, the bad castings are getting fewer and fewer but I hate it when it happens. Lots of time consuming work down the tubes.

I also heat the resin. My ultrasonic cleaner has a heater and I put in hot tap water.

Do a good turn daily!
Don
Click to expand...

Yes I remember that conversation, and after talking to you I tried it with very mixed results so I went back to CA. For some reason I guess I didn't know you were heating the PR. Last month the light bulb went off and I heated the PR before rubbing it on the skins and the couple of castings I've done were no problem with the "silvery" effect. But as you pointed out it will come back at the most inoppertune times. We've come a long way in the last 3 years with snake casting with failure rates dropping by more than 75% but we will still have them at times.
 
its_virgil said:
........then it started again...the silvery coating on the skins. ...........
Click to expand...

Man, same thing happened to me, and right after I made the snakeskin tutorial no less. It was like the 'shanks' in golf and I just couldn't shake it. No idea what was causing it but I wasted a good bit of PR and skin trying to figure it out. Just gave up for now.
 
I found a short tutorial at rodguild.com/howtos. the section on inlays gives a how to on sticking the skin down and sealing it. I have not tried this but it may help.
Mark
 
Thanks everyone for some great help and advise on the problem.It's bitter sweet to know that others are having the same kind of issues with the skins. You all have given me a lot of ammo. I'm going to set things up for another try this weekend using all of the good ideas. This is why i like this forum, great people who are willing to share. Thanks a million to everyone.
 
Might not apply to skins at all, but I know I was getting tiny bubbles in
EVERY casting I did.. nothing seemed to help. I tried coating with CA,
with un-catalyzed resin, spraying with acrylic, with lacquer, coating with
white glue. Out of maybe 50 castings, ONE came out with no bubbles.
(well, there were a couple, but they turned off)

I have been testing my own molds and dusting the mold with talc or
super-fine powdered marble, which is just as fine as talc.

I put a little dust in the mold with a small paint brush, or bang it around
like you're flouring a baking pan, dump it out and then gently blow it
out to make sure it doesn't clump up in the corners.. then cast as
usual. You're using a very small amount, might not even see it when
you're done.

I haven't had a bubble since. Not one!

I can see how the talc would reduce the surface tension of the resin, but
I'd expect that to affect only the skin of the casting. But I haven't had
one single bubble anywhere in the casting so far. (I've only done a half
dozen castings, maybe two dozen tubes and a few blocks)

I'm not sure why this works. I'm not even 100% sure that I haven't done
something else that I'm not aware of and THAT is giving me a good cast.
But I've wracked my brain and can't think of what else it might be. Why it
affects the casting anywhere except where the resin meets the mold, I'm
just not sure. You can see the powder on the outside of the casting, but
that's going to be turned away anyway so it doesn't matter.

But I'm not going to change it now.. :biggrin:
 
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