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I am using stainless steel molds and since the first fire, they continue to peel each time afterwards. Is this common in stainless steel. It is getting into my glass. When is peels, is this the same thing as spall?

Thanks for the info.

Mike Hawkins
(hoknok)
pronounced Hock-Nock as in Brock ( for those who have asked...)

Are you sure it's solid stainless steel? Stainless typically won't spall and definitely shouldn't peel unless it's laminated with something else.

Tony

I have seen the peeling stainless steel as you've described but only in a corrosive enviroment. Stainless steel doesn't melt until around 2500 F.

There are different grades of stainless and some are more resistant to corrosion than others.

You're certain they are stainless?

Are these molds specifically made for glass?

Are they flaking or are you getting crud sticking to your glass?

Can you provide details on the type of glass, firing schedule, etc.

I've been using these for pattern bars and have noticed peeling. I use ThinFire as a barrier so luckily it's not getting on the glass. But I was wondering what was causing it. I'm also wondering how many more uses I'll get out of them before they fall apart.

you should be using some sort of fiber paper anyway with these types of molds, as the steel will shrink more than the glass, and you'll need to account for the less room inside the mold.

it's probably just not a type of stainless steel that resists spalling, if it's stainless at all.

you could use cut up shelves or tiles to make dams instead, if you wanted different sized ones than what you could get from this mold. you still have to use fiber paper with these too. if you use 1/16" paper, it's reusable a few times.

SAReed wrote:I've been using these for pattern bars and have noticed peeling. I use ThinFire as a barrier so luckily it's not getting on the glass. But I was wondering what was causing it. I'm also wondering how many more uses I'll get out of them before they fall apart.

Does a magnet stick to it? If it does, there's a very good chance it's not stainless.

Tony

Tried the magnet, didn't stick. I'm sure it's stainless, but comparing it to a stainless bowl I've used for slumping that hasn't peeled, it's a lot thinner. I'm guessing it's a poorer quality of stainless. What really gets me is I paid $14 for each bar tray and it's probably $0.50 of stainless that's used. I could have had a stainless cutter and bender for free and didn't take it....how was I to know I could've used it???

well I just tried the magnet and although it did not stick to the mold its self, all the particles (metal flakes) in the mold did stick to the magnet?

Anyway, I am sure these are not the quality stainless steel molds sold for such purposes. I am using stainless steel large mixing bowls for a type of sand casting. I fire the mold up to 1500 and sometimes even to 1700 in order to melt the glass that is deeper in the sand. The molds themselves are mainly to contain the sand, not the glass. Judging by its looks, I will get another 4-5 fires before they are history. I will just have to sand them before each use to reduce the metal flakes.

As for now, I am firing organic looking pieces from glass beads for a series called "Primordial Life". Actually, sometimes the metal flakes make the piece look even more interesting. I will post these and others in the next 30 days as I get the new site up.

Thanks
Mike Hawkins
(still playing with glass)

At 1700, I'm surprised you have any mold left. Stainless melts somewhere around 1800 or 1900, so I'm sure it's gotten pretty soft by the time you get to 1700.

I don't know anyone who uses their stainless steel molds at that high a temperature.

Tony

SS melts at 2588F (1420C) What is the thickness of the steel?
This should be SS304 or possibly SS302 If the people you got it from don't know then don't deal w/ them again. If it is a scrap drop it could have been contamenated by someone grinding mild steel nearby and throwing slag on it. If you want to remove this problem, try an aggressive sandblasting and then soak a towel in vinegar, wrap the steel, put in a plastic bag overnight. The acid is a good way to remove millscale from mild steel; I've never seen this kind of thing in stainless (and I've had it in run-away kiln conditions). But that obviously doesn't mean it can't happen!
Is it peeling inside and outside the mold?

Yes, it is peeling on both sides. The stainless steel molds are bowls from a department store. They had the name ssteal on the label. They are rather thin mixing bowls that I have used to slump glass over for drapes. Since then I just use them to contain my sand and do not allow the glass to touch the edges. When is peels, is this the same thing as spall?

Anyway, thanks for the advice. I will just get a more professional version when these are done.

jerry flanary wrote:SS melts at 2588F (1420C) What is the thickness of the steel?
This should be SS304 or possibly SS302 If the people you got it from don't know then don't deal w/ them again. If it is a scrap drop it could have been contamenated by someone grinding mild steel nearby and throwing slag on it. If you want to remove this problem, try an aggressive sandblasting and then soak a towel in vinegar, wrap the steel, put in a plastic bag overnight. The acid is a good way to remove millscale from mild steel; I've never seen this kind of thing in stainless (and I've had it in run-away kiln conditions). But that obviously doesn't mean it can't happen!
Is it peeling inside and outside the mold?

Boy, I have to stop trying to quote melting temperatures from memory... and I'm not old enough to be losing that!!!

Tony

Just use a "vague-ifier" like "around" or "at about" :p I only knew exact because I googled it. But I knew 17-1900 seemed low. Melting temps are fun to think about...
The one I really find interesting though is the sterling silver VS. fine silver: Sterling is 1475F Fine is 1761F Copper is 1984F But Sterling is made by adding a little Copper to the Fine Silver. I think it is so odd how those two interact and cause the Sterling to have such a low melting temp. Where is a drunken material science major to explain this kinda crap when you really want one? (No body gets to answer "Alfred", ok?)

[quote="jerry flanary"]Just use a "vague-ifier" like "around" or "at about" :p I only knew exact because I googled it. But I knew 17-1900 seemed low. Melting temps are fun to think about...
The one I really find interesting though is the sterling silver VS. fine silver: Sterling is 1475F Fine is 1761F Copper is 1984F But Sterling is made by adding a little Copper to the Fine Silver. I think it is so odd how those two interact and cause the Sterling to have such a low melting temp. Where is a drunken material science major to explain this kinda crap when you really want one? (No body gets to answer "Alfred", ok?)[/quote]

I think I remember learning in Chemistry class that a solution will have a lower boiling point than either of the elements from which it was made. Same principle, perhaps?