snake cast update

[its_virgil]

As most of you know I have been trying to improve my snake skin casting techniques. I have just added a step to the process. I did a cast last week where I used a vacuum pump to degass the resin prior to casting. I have just turned the first pen from that cast. It turned as nicely as the other and is just as clear. The thing I liked is that every tube is useable. I am or was having problems with some of the larger tubes coming out looking cruddy and unuseable. Bue, each tube in this 10-tube cast was nice and clean and clear. I also dropped the pressure in the pressure tank when casting to 25 psi instead of the 40-50 I had been using. I had no leakage of resin into the tubes at this lower pressure. I have pictures of the steps edited and in PageMaker and will be adding text to them soon. Maybe I can get it to Jeff this week sometime. Her is a picture of the frist pen from this lates vacuum-pressure casting. I also added a picture of the back side. I've been getting emails asking about the seam side. Enjoy and comments welcome.
Do a good turn daily!
Don

 

[JimGo]

I'm now very tempted to try the vacuum and pressure method; from a purely "intellectual" perspective, that seems like it would give the most consistent and best quality blanks.

I look forward to your write-up. Will it include your entire process?

 

[alamocdc]

Don, I too am watching with some anticipation. And I like what I see.

 

[its_virgil]

<b>JimGo,
I hope this doesn't start another discussion on the physics of why this works or why it shouldn't.[][] I have progressed from casting in an open mold (and contending with BUBBLES) to using pressure(no BUBBLES but not 100% useable tubes)) and now adding vacuum and I will continue using the vacuum. I think the pressure cured the bubbles (how and why ... don't know, but it works) amd the vacuum has made the skins on every tube so far to be as good or better than any others. I'm not really sure what has been happening...but some of the skins after casting have just looked like I added bunches of crud to the skin surface...one or two tubes from a 10-12 tube cast...with no rhyme or pattern to where the tubes were with respect to each other). And the reduced pressure is producing less leakage of resin into the tubes (non this time...and that had not happened before).

I have pictures of each step that I do and will be adding the vacuum step pictures when I do another cast today or tomorrow. I am even going to try to get pictures of the no-good castings to show what problems I've had. Maybe I can get the failures to show the mess that some ended up being.

Do a good turn daily!
Don

</b>

Originally posted by JimGo
<br />I'm now very tempted to try the vacuum and pressure method; from a purely "intellectual" perspective, that seems like it would give the most consistent and best quality blanks.

I look forward to your write-up. Will it include your entire process?

 

[Joe Melton]

Don, have you tried just shutting the connections after applying the vacuum, and then letting it sit for a few minutes? In other words, using just vacuum and no pressure?
Joe

 

[its_virgil]

<b>Joe,
I degass the resin in a glass jar until the bubbles stop, then I take the resin and slowly pour it into the mold then place the mold into the tank and apply pressure. I want to try to pour the resin in the molds with the skinned tubes and apply vacuum, but I'm thinking the air sucked from inside the tubes will possible pull out the corks I use to seal the lends and the tubes will fill with resin. I should give it a try, but I may need to find a new way to seal and support the tubes. Here is how I do that now.
Do a good turn daily!
Don
</b>

<br />

Originally posted by Joe Melton
<br />Don, have you tried just shutting the connections after applying the vacuum, and then letting it sit for a few minutes? In other words, using just vacuum and no pressure?
Joe

 

[bonefish]

Don:

All I know about physics is that if you drop something heavier than air, it will fall, but I would like to make a guess of why the vacuum and pressure works as it does.

Basically, from what I can understand, when you apply vacuum, you are drawing any residual moisture out of the snakeskin. Along with removing this moisture, you are also removing air. Air bubbles are made made from air, is that correct?

The air we breathe is composed of about 85 percent nitrogen and about 15 percent oxegen. Neither nitrogen or oxygen are inert, meaning both will react with other elements and compounds. There could possibly be a reaction with the resin when you cast, but I'll leave it to a chemist to figure this one out.

But, what I think happens is that all the nitrogen and oxygen along with any air bubbles and contamination is removed by the vacuum and replaced by the resin when you apply pressure to the tank.

This would be comparable to the threads on stabilizing wood, where first a vacuum is used, then pressure is applied to force the stabilizing agent into the voids created when the vacuum pulled out the air and whatever else was in the object.

I think there is a possibility that wood could be stabilized using the same method, using PR or epoxy resin.

Next time you cast, will you also drop a piece of wood in a mold filled with PR into your pressure pot and see what happens?

Pardon me for stealing your thread, but when you made the first post, it occured to me how it might work, and knowing how something works is the first step in solving any problems that might develop. [?]

Bonefish

 

[JimGo]

Don,
How 'bout using a rubber band around your stand-offs? That will keep them from opening up when the vacuum is pulled.

I like the cork idea!

 

[its_virgil]

<b>Jim,
I actually run a bead of CA around the cork and glue it in the end of the tube. I also put BBs into the tube to keep them from floating in the resin. But, some have leaked in resin when the tank is pressurized. If the pressure can push the resin in, I would think the vacuum could pull the air out. The resin doesn't travel through the corks because when I cut them off the tubes, there is no resin inside...i.e. the corks are not stabilized. I may just have to prepare a tube and use a small mold and do the entire cast in vacuum and just see what happens. I'll report back when finished. Thanks, the corks seem to work very well. I ordered them from:
http://www.sunburstbottle.com/s.nl/sc.13/category.39/.f

Size 0,00,1,2,3,and 4 have worked on every tube I've cast from slimlines to Gents.
Do a good turn daily!
Don'</b>

Originally posted by JimGo
<br />Don,
How 'bout using a rubber band around your stand-offs? That will keep them from opening up when the vacuum is pulled.

I like the cork idea!

 

[BRobbins629]

One technique used in the lab to degas solvents is ultrasonics. Since this would be done at atmospheric pressure, it would be less likely to push resin into the tubes (something I have done more often than I care for). If someone has a jewelry cleaner available or finds an ultrasonic cleaner at a good price, this might be a good thing to try for 15 minutes or so before the resin starts to gel. I would put a small abount of water in the cleaner (about 1/4 - 1/2 inch) and place a continer of the resin, or even the mold in the water and ultrasonic away. Just another idea to add to the confusion.

 

[thewishman]

Those snakeskins are looking sharp!

 

[its_virgil]

]Originally posted by bonefish
<br />Don:


But, what I think happens is that all the nitrogen and oxygen along with any air bubbles and contamination is removed by the vacuum and replaced by the resin when you apply pressure to the tank.<b>I am only applying vacuum to the resin at this point and not to the skin also. The wooden supports that hold the skin off the mold have not been resin impregnated when i cut them from the tubes. So, just the pressure is not forcing the resin into the wood. Polyester resin cures or hardens too fast for it to be a good resin for stabilizing. It often cures or jells in 15-20 minutes.</b>

This would be comparable to the threads on stabilizing wood, where first a vacuum is used, then pressure is applied to force the stabilizing agent into the voids created when the vacuum pulled out the air and whatever else was in the object.

I think there is a possibility that wood could be stabilized using the same method, using PR or epoxy resin.

Next time you cast, will you also drop a piece of wood in a mold filled with PR into your pressure pot and see what happens?<b>es, next time I will drop one of the square standoff disks into the resing during the vacuum and put it in the mold while the pressure is applied and see if it gets stabilized.</b>

Pardon me for stealing your thread, but when you made the first post, it occured to me how it might work, and knowing how something works is the first step in solving any problems that might develop. [?]<b>No problem Bonefish. Thanks for the ideas and I will let you know what the results are.

Do a good turn daily!
Don
</b>

Bonefish


[/quote]

 

[Dusty]

Don those skin blanks are really nice and I think you are on to something. As far as the leaking into the tubes goes, have you ever tried to fill the tubes with plunbers putty? It wont stick inside the tube and when you remove them form the pot just take a dowel and push out the putty. Just a thought.
Dusty

 

[JimGo]

Gracias Don!

 

[its_virgil]

you're welcome...
Don

Originally posted by JimGo
<br />Gracias Don!

 

[its_virgil]

Thanks Dusty. No, I haven't use plumbers putty. I use modeling clay before the pressure casting, but thought it would not work with the pressure. I'll put that on my list of things to test.
Do a good turn daily!
Don

Originally posted by Dusty
<br />Don those skin blanks are really nice and I think you are on to something. As far as the leaking into the tubes goes, have you ever tried to fill the tubes with plunbers putty? It wont stick inside the tube and when you remove them form the pot just take a dowel and push out the putty. Just a thought.
Dusty

 

[its_virgil]

<b>UPDATE:</b>
<b>Yesterday I placed the prepared blanks(see earlier post in this thread) in the mold and poured the resin over them. Then I applied vacuum for 20 minutes, released the vacuum and applied 25 psi pressure until the PR kicked over. Came out very nice and the tubes did not leak...I'm excited. This will eleminate a couple of steps from the process. I'll turn the pen this evening or tomorrow and post a picture.
Do a good turn daily!
Don</b>

Originally posted by its_virgil
<br />As most of you know I have been trying to improve my snake skin casting techniques. I have just added a step to the process. I did a cast last week where I used a vacuum pump to degass the resin prior to casting.

<br />

 

[johncrane]

looks realy good Don