What's Happening Here?

[fiferb]

A little background: I'm using PR over painted tubes, cast in the Wal-Mart ice trays. Pressure is about 15psi. If you look under the clip (where I tried to hide it) you can see an air bubble that runs the length of the tube and is right on the tube. It doesn't come to the surface and is very shallow. From the top it is a shiny area but clearly jumps out as an air bubble from the side.

Any ideas? Thanks for any comments and help.

Image Insert:

 

[Jeff-in-Indiana]

what kind of paint was used on the tubes ? ?
I have cast some powdercoated tubes in resin under no pressure and they were bubble-free .. could water have crept in from one end while you wet-sanded (making an assumption there) through maybe a paper-thin 'disconnect' between the paint and the resin ??

nice color/resin combo, by-the-way

 

[fiferb]

Jeff, I don't wet sand so that is not the issue. The PR is clear. The color is painted on the tube. It was dry for many days, probably more like weeks before I cast it.

 

[Blind_Squirrel]

It looks like the PR has come loose from the tube.

 

[Jarheaded]

Is it possible that you accidentally put too much pressure on the blanks while you were setting them up on the mandrel? It only takes a little bit of pressure to cause a kink in the tube that would not be visible to the eye.

 

[fiferb]

Originally posted by Jarheaded

Is it possible that you accidentally put too much pressure on the blanks while you were setting them up on the mandrel? It only takes a little bit of pressure to cause a kink in the tube that would not be visible to the eye.

No, they came out of the pot this way. I thought it was a shadow at first or a dark spot from the paint.

 

[fiferb]

Originally posted by Blind_Squirrel

It looks like the PR has come loose from the tube.

OK, I'll buy that. Any idea what causes it or how to prevent it?

 

[Blind_Squirrel]

Originally posted by fiferb

Originally posted by Blind_Squirrel

It looks like the PR has come loose from the tube.

OK, I'll buy that. Any idea what causes it or how to prevent it?

That is something that I am still struggling with too. I use powder coated tubes and this sometimes happens to me. When it gets warm enough to get back out in the garage and do more casting I am going to try dipping the PC'd tube into thin CA. Let the thin CA set up, then cast the tube.

Up to this point I have not scuffed the PC either. I will also try hitting the PC with some 400 grit sand paper to give it some tooth.

Frustraiting as H311 when this happens because I don't notice it until AFTER I have the blank turned and polished. [B)]

 

[fiferb]

Thanks Scott. I don't think scuffing will be an answer in this case as these are not PC'd and would take the paint off. I wonder if Alumilite would work better than PR. May have to try.

On the next I may try your thin CA trick. I have another pen I cast at the same time as this that has the same problem. Different materials inside. It also has bubbles. I sprayed a coat of Deft laquer in it to try to keep the decal from lifting. It didn't work. I'll have pictures of it later.

 

[gketell]

What it looks like to me: your paint softened and mixed with the PR during casting almost everywhere, but in those few spots it didn't so you have clear PR.

Think about it, if it is clear and you are looking from the side then you should be able to see through it for the entire thickness of the PR. If you can't see through it, it isn't clear.

If your paint stayed ON the tube and your PR was truly clear OVER the paint you would have had a clear area across the entire tube when looking from the side.

GK

 

[Jarheaded]

I have painted several tubes, then cast them in Alumilite and it has worked out well for me. I have had some problems earlier with the labels peeling and after using Elmers white glue over them, the problems were gone.

 

[oldtoolsniper]

I know with wood finish and car finish of the lacquer type you get what’s called fisheye from contaminates on the base wood or metal. It means the finish just won’t adhere to certain spots. Could this be fisheye with resin?

 

[fiferb]

Originally posted by oldtoolsniper

I know with wood finish and car finish of the lacquer type you get what’s called fisheye from contaminates on the base wood or metal. It means the finish just won’t adhere to certain spots. Could this be fisheye with resin?

Could be. I had my fingers all over the tube getting it ready for casting. Next time I'll wipe it down just to be sure it doesn't have any contaminates.

Thanks.

 

[Firefyter-emt]

FWIW.. The air pocket is from the shrinkage of the PR. The PR shrinks when it dries and can become smaller, thus causing the hole for the tube to become larger.

I aam going to give the Alumilite and see if that solves the problem.