corking molds

[Pete VanderLaan]

I got this as a private message and I don't yet have time to find the thread. Perhaps someone can do the simple search. It seems to me it was this:
http://talk.craftweb.com/showthread....=corking+molds
*****

Originally Posted by pierre bowring

Hey how are you? I can’t seem to find the article Ed skeels wrote on corking steel molds. Also a guy I know told me Taylor kurle put a really good article up on corking steel molds with renite and can’t seem to find that either. Could you help me out? Finally, I know sorry this is a lot, I was curious if there was any info on mold blowing? Again have looked numerous times can’t seem to find anything. Thanks so much!

[Shawn Everette]

Not the thread but here's Mr. Wizard's instructions.

[Charles Friedman]

It helps to heat up the metal mold a little first, before adding the linseed. It helps with getting an even layer, let it drip upside down till it cools and gets real tacky, then apply the cork dust. And repeat 3 times.

[Jordan Kube]

Forget the linseed oil. Use Renite. Ed switched to that.

[Eben Horton]

I corked a 12” wides 32” cylinder mold with linseed oil. Dropped a bubble into it the first time and as I pulled the bubble out, the linseed oil vapors combusted and shot the bubble and pipe up about a foot in a giant cannon blast. Scared the crap out of me.

[Greg Vriethoff]

Here
^^^^^^

[pierre bowring]

Thanks man!

[Robert Melvin]

Thank you very much. This is very relevant to some questions I have right now.

What about preparing a mold interior with a plating of some ratio of gold-platinum or some other material? I read that gold-platinum was used in industry to create process features hot glass will not stick to.

I would love to be able to send a file to a machine shop, get an aluminum mold back, get a plating on it, and use it to mold gobs of glass by pressing into a female mold with a male core.

Being able to take billet glass and convert it to finished parts or preforms would be great and I would appreciate advice.

Originally Posted by Greg Vriethoff

Here
^^^^^^

[Tom Fuhrman]

If you are looking to run vary much production from that mold I would suggest you use a steel mold instead of aluminum for pressing. The mold will get hot very quickly with aluminum and steel will last a lot longer and you will want to devise some way of cooling the mold in between pressings. The press shops usually had direct air blowing on the molds from several directions to help with cooling. check out some of the old side lever pressing operations for some pics. BTW I have a friend who is selling an old side lever press in the Midwest if anyone is interested.

[Michael Ahlefeldt-Laurvig]

aluminum melts at 550 C glass is at least 1150C

[Sky Campbell]

Originally Posted by Michael Ahlefeldt-Laurvig

aluminum melts at 550 C glass is at least 1150C

The melting point of aluminum is 933.47 Kelvin, 660.32 degrees Celsius, or 1220.58 degrees Fahrenheit.

Aluminum does work well for many glass related applications but press molds would have to be water or air cooled and certainly not the best solution for long term use. That said how many molten gathers have I stuck into aluminum optic molds? literally thousands upon thousands.

[Shawn Everette]

I've heard the story in person, and read it in the Bathroom Reader, about the student at Chuck that wanted to warm the mold to pick up cane. The TA was more interested in t&a and blew off his questions. So the kid sticks the mold, that was welded to a plate with all the other molds, into the kiln to warm up. 30 min later the TA finds the puddle in the bottom of the kiln. I was always curious who tf put the set point high enough to melt aluminum.

That being said, I had an instructor that used an aluminum cane plate as a pastoreli on forks, that did not end well.

[Michael Ahlefeldt-Laurvig]

Well I was wrong then but I have a homemade type high temperature fuse in my annealer that melts at 550C if the controller fuses the contactor and runs away from me
Maybe a special alloy then?

[Pete VanderLaan]

we lost an iron fero at Pilchuck in one of the tanks. I won't say what the illustrious person's name was but we put up a sign saying "Bethlehem Green" next to it.

[Tom Fuhrman]

Originally Posted by Sky Campbell

The melting point of aluminum is 933.47 Kelvin, 660.32 degrees Celsius, or 1220.58 degrees Fahrenheit.

Aluminum does work well for many glass related applications but press molds would have to be water or air cooled and certainly not the best solution for long term use. That said how many molten gathers have I stuck into aluminum optic molds? literally thousands upon thousands.

Glass plunged into an optic mold normally has a cooler skin on it than the glass you are gathering and dumping in a press mold. One normally doesn't expect the aluminum mold to absorb the heat as a press mold does. The mold is made to turn the glass from a semi liquid state to a solid mass. different physics are involved than plunging into an optic mold. Optic molds can take it because we normally don't dump semi liquid material into it except on rare occasions.

[Monte Becker]

The theory is hearsay. The facts support it...

I understand that the skin of aluminum is aluminum oxide, which melts at a higher temperature then "pure aluminum" (??) on the inside of the mold. The idea is that the inside becomes a liquid at a lower temperature than the outside.

Someone took my aluminum mold and brought it up to 900F. It did indeed have a hernia (spludged out the side and made a 1"x3"x1/4" puddle). The business part (the inside) and the outside look and appeared fine.

But one has to wonder if the internal void will ever cause me trouble. So far, so good...

[Shawn Everette]

Unless your mold was a very low temp alloy, or had a contamination, it really should have done nothing in a 900* kiln. A good foundry melt should be pretty consistent throughout the entire product.

You are correct in that the oxide layer melts considerably higher, about 3200*, but the naturally occurring oxide layer is not going to be thick enough to support a hollowed out core under any kind of stress.

[Pete VanderLaan]

the section of that mold may have had a void to begin with, allowing the area to get hotter faster.

[Shawn Everette]

I could understand maybe a 100* difference as the coils go full rage, but 300* seems a bit much. Realistically if it reached melting temp the whole thing should have collapsed. I have a couple molds I hate that make me really want to test this.