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Building Wax models for Casting

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Building Wax models for Casting

Postby Twin Vision Glass » Tue Jun 08, 2010 12:48 pm

Hello to all. I was wondering this the other day. Someone asked me how to create a large wax vessel form in hollow format. I usually create hollow forms in about 4 different sections and then weld them all together , to create very thin LARGE waxs to then transform into glass. I thought it would be fun to start a dialogue with all you casters out there, what is your favorite way to get 1/8th thick hollow forms for glass casting. I look forward to this discussion.
Leslie
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Leslie Rowe-Israelson
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Re: Building Wax models for Casting

Postby kgkennedy » Wed Sep 22, 2010 10:48 am

Hello Leslie - What do you mean by large size casting? Do you mean something that is 6" or 16"? What are the size constraints on your kiln? What are the time constraints on your heating and annealing programs?
This is what I know. Generally, even with the best venting through the mold that you can imagine or devise - without compromising the integrity of your investment- it is extremely difficult to investment cast anything that has 1/8th inch walls. Lead crystal is about the only media that will run thin enough at high temperatures. If you don't vent well it won't run no matter how long you hold it, and you run a serious risk of devitrification with long holds at high temps, especially if you are using a solid investment core to make your hollow interior.
Sure, Emile Galle cast thin walled vessels. But he did it by having interlocking removeable core forms that were placed inside the molds after the outside face of the vessel was packed with frit. This way he had a hollow interior core form that allowed the glass to heat quickly, without the insulating properties of investment slowing the firing down. He didn't have to worry about venting a flow, because the glass was already in place.
But investment casting a solid vessel with 1/8" thick walls means you have to use a reservoir, you have to create venting that allows all that interior air inside the mold to escape and the glass to flow, and you have to think about a mold core that is not going to resist heating and can remain stable inside the flowing glass, and that you will have to hold your firing at high temp for a long time, and cool it very slowly. You can check Henry Halem's 'Glass Notes' for a good annealing cycle. I think his cycles are a little long, but better to err in favor of caution. But there is nothing more frustrating than to fire and anneal over a week, then wait a week before opening up a mold only to find the empty walls of the impression of your work because the glass didn't flow due to poor venting or thin walls.
kgkennedy
 

Re: Building Wax models for Casting

Postby kgkennedy » Wed Sep 22, 2010 10:58 am

Leslie - another thought. You will have to control the thickness of the walls very carefully so they are uniform. And you will have to think about the form because of the way the glass contracts as it anneals. Both of these issues affect whether or not you will be able to successfully anneal your piece, because both cause irregularities that can contribute to stress.
kgkennedy
 

Re: Building Wax models for Casting

Postby Twin Vision Glass » Wed Sep 22, 2010 8:26 pm

Hi!!!!! sorry I have been away from computers for some time now BUT am back home now and just noticed you had responded. Thankyou. I am really talking about just the WAX though. :) I have already cast this vessel in glass, and the glass was actually quite thick walled; so the discussion was meant to discuss creating hollow WAX vessel forms for the lost wax casting process. Sorry if I was not very clear. The wax is on the LOWER section of the picture. I like to try to make all my wax hollow!
http://www.twinvision.fusedglassartists ... urney.html
Leslie
Leslie Rowe-Israelson
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Re: Building Wax models for Casting

Postby kgkennedy » Wed Sep 22, 2010 10:19 pm

Leslie - let me see if I have this right. You want to make the wax model itself hollow. So that the wax is lighter, you use less wax, there is less wax to melt out. You want the original wax to be hollow.
When I look at the photo of your wax...how big is this anyway?......
The only way I know to make a hollow wax form is by making a master parting mold of the object, basically making it possible for you to duplicate the form. You need to leave an access to pour the wax in, and small vents to let the air out. You can do this the same way that you might make molds for making waxes for metal casting, either by making a multi-part interlocking plaster mold that you would then soak, rubber band together, and fill with hot wax, then pouring out the still liquid warm wax, leaving a residue of wax inside the master mold, which would then be disassembled, and any flashing of the wax, or pitting of the surfaces being cleaned up with hot tools and polishing. AND THEN you could invest the hollow wax. Or you could make a one piece latex mold - using the original piece as the model - and then make a multi-piece plaster mother mold - to keep the latex stable and in place while you pour in the hot wax to coat the interior of the latex mold - then take the mother mold off, cut open the latex, pull out your original, put the latex back in the mother mold, fill and decant the hot wax, then disassemble the mold, pull out your hollow wax, clean it up, and then invest it for casting. The best reason for going through all these steps is to be able to make a series of the same objects, or to make sure you have a source for more wax models in case you have incomplete castings. It's a lot of work, and if that piece you have is as large as I think it is, you will end up with a monsterous undertaking involving lots of process materials, time, and physical labor. You could make the multi-part plaster mold, then coat the individual components with wax, and then assemble them, but it still means you need a wax -or clay, or wood, or whatever media - original piece to make a parting mold from.
You can make flat, thin sheets of wax by melting your wax and then pouring it into a wet plaster mold of a walled baking sheet, and then construct your piece using these thin sheets, tacking them together with a soldering iron, and building them leaving a hollow cavity inside (think of hollow chocolate easter bunnies - which is a good example of the use of parting molds and casting in series). Or you can take the same walled baking sheet, spray it with a good coat of water, and then pour wax to the thickness you want for your sheet, and pour your wax that way. I think the plaster mold is best, make sure it is soaked..meaning no bubbles venting from the submerged plaster.
After you get a hollow wax you will want to make sure that it is uniformly thick, and sealed. So you should check it by shining a flashlight inside to see if you can see the light from outside, and vice versa.
But I would be concerned about wall strength of hollow waxes, and also leaky joints where the wax meets up, because you don't want your investment leaking into the hollow cavity, or deforming your walls. That seems like a really big complicated piece that you are working on, and it seems you already have so many factors to control that maybe you don't want to make this any more complicated. Some one said to me 'it's easier to make the wax right than it is to try and fix the cast piece.' You Know?
You can check mold making processes for metal casting, or ceramics because slip casting is handled the same way. Think about it, find good pictures of the process, draw your ideas out, plan the whole process on paper, decide if it is worth all the extra work. This process is good for components that are repeated, and basic forms upon which you can make variations. They are generally a stock resource, not useful for a single shot. Good Luck, and a hug.
kgkennedy
 

Re: Building Wax models for Casting

Postby jerredavidson » Thu Sep 23, 2010 10:05 am

Hi Guys,
I was in a workshop with Irene Frolic in May, and we filled a large balloon with water and diped it into the wax until it reached the desired thickness. We then cooled it in a bucket of water and let the water out of the balloon. Voila we had our model for a thin walled vessel. You still need to make and attach a cruicible for the glass and make sure you allow enough time for the the glass to flow but otherwise this method should work. You may also need to vent depending on the orientagtion of your vessel. The only other way I have cast a vessel was using a 4 part mold and the walls were quite thick.
jerredavidson
 

Re: Building Wax models for Casting

Postby Twin Vision Glass » Thu Sep 23, 2010 11:47 am

Hi!!! I love this interaction and discussion. Yes the piece is already made. I just wanted others to think about how to make LARGE one of a kind vessel forms. It is quite thick ! BUT the wax was truly fun to make. Many ideas you have presented where followed in the creation of this glass vessel.
http://www.twinvision.fusedglassartists ... urney.html

I use alot of plaster molds I have created out of clay first too and also pour thin ( aprox. 1/4 inch thick) bits and pieces and WELD together like you mentioned. I tooo follow many ways that Irene Frolic and Lou Lynn from Canada work. Many years ago they changed my thinking towards one of a kind vessel forms. Lou is a master with Wax and I love to watch both artists create with wax. I also have a hot plate with semi-melted wax that I scoop out and slather onto the constructed vessel ,(and then tool and shape with a special wax tool with different shaped tips that are heated) and also seal all seams that I have created by welding the parts together. I love to work this way, and unfortunately the Portland , Oregan glass guild only had ONE day when I was showing them how to create this way. I love the dialogue and techniques you have shared , and will hunt down some photos for you also to show you visually what I am trying to describe. Thankyou so much for your input in this thread.
P.S. the walls of the glass finished vessel are a consistent 3 inchs thick.
Leslie Rowe-Israelson
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Re: Building Wax models for Casting

Postby Twin Vision Glass » Thu Sep 23, 2010 12:19 pm

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One wax hollow vessel form (to look like a birds nest and twigs and leaves) that has been created by applying bits and pieces of wax designs carved prior too! and more little images carved into larger sections of semi melted wax that was applied to the hollow vessel.
Last edited by Twin Vision Glass on Thu Sep 23, 2010 8:07 pm, edited 1 time in total.
Leslie Rowe-Israelson
Give out FREE hugs!
Twin Vision Glass
 
Posts: 567
Joined: Wed Feb 04, 2009 4:42 pm
Location: Invermere , B.C. Canada

Re: Building Wax models for Casting

Postby Twin Vision Glass » Thu Sep 23, 2010 12:27 pm

Image
A many part mother mold of a bear sculpture that is poly-urethane, and then I will pour wax and make 1/4 inch wall of wax. Then carve the wax tooo when it comes out so it is different and unique. If I want to carve the wax in certain places I will paint on more wax INSIDE to make it strong in that section. Next picture will be the wax hollow bear.
Les
Leslie Rowe-Israelson
Give out FREE hugs!
Twin Vision Glass
 
Posts: 567
Joined: Wed Feb 04, 2009 4:42 pm
Location: Invermere , B.C. Canada

Re: Building Wax models for Casting

Postby Twin Vision Glass » Thu Sep 23, 2010 12:32 pm

Image
I use alot of older wax tooo that I have re-constituted to keep costs down and in creating hollow forms ;it is also not as heavy while moving around.
Leslie Rowe-Israelson
Give out FREE hugs!
Twin Vision Glass
 
Posts: 567
Joined: Wed Feb 04, 2009 4:42 pm
Location: Invermere , B.C. Canada

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