Burn out the wax

[imraslan]

HI, i am preparing a glass model that is narrow from bottom and extend upward with many undercuts/turns and narrow edges. after I pour the plaster mold on it, what is the best way to burn out the wax putting in mind I don't have a klin at home not do i have a steamer.

I read that I can place the plaster in a pan filled with 2 inches of water and boil it so the steam can burn out the wax, or alternatively place the plaster over a gas burner. I have tried the second method before, but the mold turned black from the fire at some points, wouldn't that affect the casting? also how do i make sure all the wax is gone completely since I can not check the wax through the narrow holes

Appreciate the advice

Imad

[Alexis Dinno]

HI, i am preparing a glass model that is narrow from bottom and extend upward with many undercuts/turns and narrow edges. after I pour the plaster mold on it, what is the best way to burn out the wax putting in mind I don't have a klin at home not do i have a steamer.

I can't help you with that as my lost wax experience is pretty limited, but . . .

I have tried the second method before, but the mold turned black from the fire at some points, wouldn't that affect the casting? also how do i make sure all the wax is gone completely since I can not check the wax through the narrow holes

The black is soot—organic carbon. When you cast the glass your are going to be reaching temperatures which turn that soot into air. Same for any remaining wax (it's not good for your kiln elements, but technically you can leave the wax in place and just let the glass pour in from above the mold for this reason). As long as your schedule moves slowly enough, that gas should have time to escape rather than being trapped as bubbles. Depending on the shape of your piece you might need to drill some air release holes if some gas could be trapped (i.e. air from before the mold was fired, or from after the soot and any residual wax gassify).

[Brock]

. . . you can leave the wax in place and just let the glass pour in from above the mold for this reason . . .

Hmmm . . . not in my experience. Begging for problems . . .

[Yardic Glassworks]

Put a couple inches of water in a pan, place your mold above the water using something like shelf posts, boild the water and steam out the wax. I like using a big pot with a lid. Some people fill with glass at this time and include their drying schedule in the ramp up. I prefer to dry my mold and burn out the wax before I fill the mold with glass. I have a friend who uses an old barbque and places his big pan of water on that and closes the lid while the wax steams out.

[Morganica]

If your wax has a petroleum base (such as brown "victory" wax) and your kiln is in an enclosed space with limited ventilation, do NOT burn it out. The fumes are extremely acrid. I did a kiln burnout in my studioexactly ONCE with a mass of victory brown--experienced extreme respiratory distress, burning eyes, etc., and spent the rest of the day airing out the house. The smoke leaves an oily brown deposit on everything, which stains cloth and is a pain to scrub off.

You can torch wax out in an open, well-ventilated space (i.e., outdoors), but be careful if your mold is plaster: When the flame touches the mold plaster it can rapidly evaporate the water and open cracks in the mold, rather like a dry lakebed. It takes a bit of practice to aim the flame only at the wax and avoid the plaster.

Glass Hole's method works well, although it helps to direct the steam to the wax and not to the whole mold if you're removing a lot of wax. Otherwise, you risk saturating the plaster and turning it soupy, which can weaken the mold, cause loss of detail and sometimes makes the surface of your glass scummy.

I started out steaming by buying an old used spaghetti pot at the Goodwill. It worked well for smaller pieces.

For bigger pieces (that wouldn't fit in the pot, which was most of them), I drilled a hole in the lid, got heat-resistant tubing (actually, I found an old clothing steamer hose at the Goodwill), and pushed it through the hole. I filled the pot with water, put the lid+hose on the pot and duct-taped the entire assembly together. Then I bought two big galvanized washtubs and a stainless steel rack salvaged from an old oven. I put the rack on the first washtub, put the mold on it, stuck the hose in the mold and then covered the whole thing with the second washtub. Steamed the wax out pretty quickly without messing up the mold. The wax drips down into the bottom tub; if you put a little water in the tub before you start it never sticks and is fairly easy to remove.

Now I've got an old wallpaper steamer (also bought at Goodwill for about $15) that I use in place of the spaghetti pot.

One other tip (which I learned from Mel & Les Israelson): Make your waxes hollow for anything larger than jewelry-sized pieces. The wax steams out in a fraction of the time and is much less damaging to the mold.

[imraslan]

Thank you for all the advice and I like the idea of making the wax hollow I will try it, I guess there is no way to check if all the wax is gone, is it ok if there are some wax still left over? will it affect the casting?

[Morganica]

If a petroleum-based wax doesn't completely burn out by the time the glass comes down, it can be trapped in/near the surface of the piece. Looks a bit like burned mercury and has to be dug out.

Little smears of wax on the mold aren't usually a problem--they'll burn out before the glass softens. If you've still got wax in the mold after you've been steaming awhile, remove the mold and fill it with boiling water. Let it sit for a couple of minutes. The wax left in the mold will melt and rise to the top. Skim it off and pour out the water.

[twin vision glass]

How big is your piece. Do you have access to a wall paper steamer or pressure pot. The wall paper steamer is best as it has a long hose . Cut a hole in a piece of wood that will accept the hose. Set it up on a rack over a container that will capture all the dripped wax. Make sure once the wax starts to run it has somewhere to drop all the wax into the container below. Also good advice is to cut 2 strips of wood that is 1/2 an inch higher than the wood with the hole so your mold sits up abit higher than the piece of wood to keep the top of your mold nice and clean.
Place mold on the wood which is suspended above the container to catch the melted wax and water. (make sure the hose is pointing straight up and at least 2 inchs into the mold itself. If you have to , secure it there with wire so it does not move when hot and pumping out steam. NOW cover whole thing with black plastic bag. Also put a blanket over to really keep the heat in.
Once the mold is truly HOT (by feel) and NO MORE WAX is coming out!) you can cool it down by unplugging the steamer AND take blanket and plastic bag off. This can take anywhere from 10 minutes to 2 hours depending on the size and shape. Do not worry, the mold will stay together. BUT let it cool. If you are worried about wax in pockets, do as my friend Cynthia suggests and pour BOILING water into mold and all the wax should rise to top. But once again waite until mold is cool . Be very careful with the mold also.
If all your vents and sprues are in the right places and under neath all the overhangs, the glass should fill and NOT capture air. Make sure you have these vents as once the glass begins to flow down, it pools and can capture air if the air has no where to escape.
I look so forward to hearing and seeing pictures. Perhaps you might send us all a picture of the wax.
Sincerely, Leslie

[Jeff Wright]

If you've still got wax in the mold after you've been steaming awhile, remove the mold and fill it with boiling water. Let it sit for a couple of minutes. The wax left in the mold will melt and rise to the top. Skim it off and pour out the water.

I recently learned a nice extension to this technique from Richard Whiteley. Pour the very hot water into the mold and wait a minute or two. Skim off the wax floaters carefully with a spoon or similar. Note that I didn't use boiling water but very hot, like you'd use for a steaming hot cup of tea. Then carefully dump the water out of the mold - it will be hot so wear rubber gloves and be careful. Now the "trick" - fill the mold with cold water. I just used cold tap water. Any remaining little bits of wax just popped off as they contracted. I was very skeptical but it really got a lot of crud out that the steamer didn't. It was a very clean mold and it came out of the kiln beautifully without some of the scum on the surface of the glass I've seen in the past.

[Morganica]

If you've still got wax in the mold after you've been steaming awhile, remove the mold and fill it with boiling water. Let it sit for a couple of minutes. The wax left in the mold will melt and rise to the top. Skim it off and pour out the water.

I recently learned a nice extension to this technique from Richard Whiteley. Pour the very hot water into the mold and wait a minute or two. Skim off the wax floaters carefully with a spoon or similar. Note that I didn't use boiling water but very hot, like you'd use for a steaming hot cup of tea. Then carefully dump the water out of the mold - it will be hot so wear rubber gloves and be careful. Now the "trick" - fill the mold with cold water. I just used cold tap water. Any remaining little bits of wax just popped off as they contracted. I was very skeptical but it really got a lot of crud out that the steamer didn't. It was a very clean mold and it came out of the kiln beautifully without some of the scum on the surface of the glass I've seen in the past.

Good idea, Jeff! I've gotta try that.

[imraslan]

Thanks All, these are great advices, I will look for a steamer to make things easier i guess and will definitely pour the boiling and cold water out. I am starting a new product line for making perfume bottle tops and caps and most of them are around 3 inch by 3 inch size (around with complicated designs and undercuts will send a pic once i have them done). Wish me luck and thank you