Using Steel Bars for molds

[Nancy Juhasz]

I have available to me different diameters and lengths of steel bars not SS. These bars would run from 2-6 inches in diameter and from about 1-6 inches in length. My question is can these be used succesfully to slump over? I am thining of laying a bar on its side and slumping over it to get a curve I don't want the shape of a bracelet mold. I am also thinking of using a piece of this that is about an inch thick on kiln posts to drape over. Do you think that the mass of the steel will make the glass crack either on the way up or the way down also do you think the expansion of the glass and steel will be compatable meaning will the steel contract faster than the glass so that the glass doesn't crack in the cool down. What firing schedule would you suggest? I was thinking of going up at about 300 dph with 10 min. holds every 200 deg. to 1000 deg. then 600 dph to 1220 deg. or slump then flashing to 1000 deg. then annealing at a drop of about 70 dph to 750 deg. then let kiln cool on its own unopened til room temp. Is this in the ball park?

[Mike Byers]

I've had good success using various non-stainless steel parts for forming glass. Disc blades, cultivator sweeps, sickle guards, etc. are all readily available around here; one of the advantages of living in a farming community. There are treasures behind every barn! My technique is to clean the parts with a wire brush wheel and then heat them in the kiln and give them a good coat of shelf primer. Heating the parts first makes it much easier to get a good coat of primer, as the water will quickly evaporate when the steel is hot. Around 200-300 degrees F seems to do the job. But non-stainless steel will still oxidize when you're slumping glass over it, so it's necessary to clean off all the rust and flaking primer to use the parts the next time. I'd avoid plated steel, as the plating is likely to outgas toxic fumes when heated. The firing schedule will depend upon what you're making, and the type of glass you're using. The things I've done have been assemblies of various parts where the glass isn't in contact with large masses of steel, and I try to insure that the expansion and contraction of the steel won't tend to "trap" portions of the glass and cause cracks as the glass and steel cool. I have slumped glass over fairly large granite blocks--a tricky process because the differing COEs of glass and granite tend to cause both the glass and granite to crack, and there is a lot of thermal mass to contend with. But sometimes I can get it to work... My advice would be to try some experiments using scrap float or another inexpensive glass. You can certainly get some interesting effects by slumping over steel, but it's important to be sure you can separate your glass from the "forms" when it's been annealed and cooled. Don't be afraid to experiment.

[Bert Weiss]

I have available to me different diameters and lengths of steel bars not SS. These bars would run from 2-6 inches in diameter and from about 1-6 inches in length. My question is can these be used succesfully to slump over? I am thining of laying a bar on its side and slumping over it to get a curve I don't want the shape of a bracelet mold. I am also thinking of using a piece of this that is about an inch thick on kiln posts to drape over. Do you think that the mass of the steel will make the glass crack either on the way up or the way down also do you think the expansion of the glass and steel will be compatable meaning will the steel contract faster than the glass so that the glass doesn't crack in the cool down. What firing schedule would you suggest? I was thinking of going up at about 300 dph with 10 min. holds every 200 deg. to 1000 deg. then 600 dph to 1220 deg. or slump then flashing to 1000 deg. then annealing at a drop of about 70 dph to 750 deg. then let kiln cool on its own unopened til room temp. Is this in the ball park?

Nanc

I would rather hear that you were using tubing than a 6" diameter solid steel bar. I would drape the steel with 1/2" fiberfrax blanket it I were using it. I hate to mess around heating up that kind of mass.

I don't want to be the one to discourage you from experimenting. Let us know about good or funky results and maybe somebody will have a good solution or approach.

[watershed]

I'm with Bert, even if you go down to fiber paper. I've seen some castings, made into a rebar cage lined with frax. The more detail you want, the more risk of undercuts etc.

Greg

[Linda Reed]

I use a regular steel wok to slump into (I do the heat and spray with shelf primer method - the outside flakes, but I've used it many times with the original seperator still intact) and I often use fencing or chicken wire with fiber paper over to create shapes, but those are both (especially the wire!) thin so they don't hold the heat so much.

When you use something heavy like farm equipment, do you do anything different with the cool down so that the glass doesn't cool much faster than the steel? Or does the steel hold enough heat against the glass that they pretty much cool together in a fairly tight kiln?

Thanks,

Linda

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[Linda Reed]

I use a regular steel wok to slump into (I do the heat and spray with shelf primer method - the outside flakes, but I've used it many times with the original seperator still intact) and I often use fencing or chicken wire with fiber paper over to create shapes, but those are both (especially the wire!) thin so they don't hold the heat so much.

When you use something heavy like farm equipment, do you do anything different with the cool down so that the glass doesn't cool much faster than the steel? Or does the steel hold enough heat against the glass that they pretty much cool together in a fairly tight kiln?

Thanks,

Linda

[lohman]

I bend candle wraps and wall sconce lighting fixtures on steel pipe.
I had a welding shop split the pipe lengthwise and I use both kiln wash and 1/16 inch fiber paper as separators.
I acquired some pipe used for fire protection systems in large commercial building and it doesn't seem to scale as much as other steel.
The scaling of course can be a problem but I've found it possible to fill bare metal scars with dry kiln wash. Personally, I like the texture that developes over time on these molds and on occasion I slip-trail kiln wash on them for added interest.
My firing schedule is the same as for slumping 2 - 3 layers of BE with the exception that the max heat might vary with individual kilns. Test and if you have a window in your kiln take advantage of it.
See my candle wraps and wall sconce in the photo section.
It's the post called "Testing my pic posting skills"

[Nancy Juhasz]

Thanks everyone this is the information I am looking for. I will let you know my results. It will be awhile until I get the bars gathered up. I don't think I will go as big as I had originally thought of going.

[Mike Byers]

When using farm machinery parts, I stack these up in the kiln so as to form the shape I want. There may be quite a bit of steel in the kiln, but the glass only contacts it in a few places: it's the outside shape of the "stack" I'm interested in. I haven't had problems with the thermal mass of the steel, but I've found you have to check frequently to be sure the glass doesn't slump too far into the stack and thereby create shapes that can't be removed after the glass cools. I've had very good success with using disc blades to form bowls (you have to weld in a piece about 1" square to fill the hole in the disc blade and then grind the weld bead to get a smooth surface for the bottom of the bowl). Another technique is to cut slots and holes in the blade with a plasma torch, and then slump glass into these slots and holes. After annealing, the glass is removed and a bracket to hang the blade is welded on. Then the blade is sandblasted, treated with hydrochloric acid (to give it an even coat of rust) and coated with a clear finish. The glass, a circle of neon and a small electronic transformer are installed on the inside of the blade to make a lighted wall sculpture. These are heavy, but the effect is interesting and people seem to like them very much. And in my part of Indiana, I have an infinite supply of old disc blades in various sizes. 30" diameter is the biggest I've found so far, and while the edges of the blades I get from local farmers are often ragged, these can be cleaned up with a plasma torch and a grinder. Disc blade steel is very tough: you'll need good bits, cutting fluid and a drill press if you need to drill very many holes.