At what temperature do the sparklers start to fly?

[bigb]

I am making something with mild steel that will have holes that I want filled with glass. A friend has a very nice, large electric kiln. She will run it up to 1500 degrees F to melt the glass. The kiln has the element wires on top, over the work pieces. I do not want the risk of sparklers damaging the element wires. At 1500 degrees F is there any chance of sparklers?

[Steve Sells]

no

[Alan Evans]

At 1500˚ C you would be having a show perhaps.

Alan

[ThomasPowers]

1500 degF is getting into a working temp not anywhere near a burning temp.

[bigb]

OK thanks guys. Looking at a heat color chart it says that scale falls off iron freely at 1750F and mild steel burns at 2400F. So since sparklers are an indication that your work is starting to burn I deduce that to mean sparklers begin to fly around 2400F?

[ThomasPowers]

don't forget to keep the "mild steel" in the statement High Carbon steels burn at a lower temp than mild.

[Frosty]

What kind of glass are you using and how melty do you want to get it Bob? One of our guys is darned food at slumping marbles. I tend to get everything too hot and actually melt the glass. You aren't likely to find anything much stickier and stringier than melted glass, the stuff sticks to EVERYTHING. I bought a tube of glass work "noodles" in a variety of colors to melt into spread crosses and other stuff.

I've had mixed results, best if I don't actually melt the glass, getting it hot enough to slump and stick together is better but melted makes a mess. Sometimes an attractive mess but . . . Pictured below is one of my more successful attempts.

Frosty The Lucky.

[ianinsa]

At 1500f you can slump glass into it but you are going to need a few hundred degrees more to 'blow into it the trick will be getting the glass and the metal to 'ramp' down at the same rate to prevent the glass from shattering.

[BIGGUNDOCTOR]

Ianinsa brings up a more important issue, tempering the glass. Glass is under a lot of stress after being formed, and needs to be ramped at a controlled rate to keep it in one piece, or in a condition that will be safe to handle. If the kiln is digitally controlled it can be done, but it will take awhile. I have. a friend who is a glassblower, and some of his large parts take days to cool down in the kiln.

Contact a glass workshop to get that info.

[Frosty]

Annealing the glass is important but it's not as tricky as most folk think. Two points to consider when mixing glass and steel, they both have similar COE, not the same but close enough. The real buggaboo is thermal conductivity, the steel will cool much faster than glass. You keep them in an environment that cools everything at the same pace.

Another little trick is using the right kind of glass. Lamp work glass is a lot less sensitive to stresses and requires less annealing.

When describing what I was doing to glass folk they all seemed to assume I was enclosing the steel in the glass not the other way around and even after showing them an example some just couldn't get their heads unwrapped from their initial assumption.

No NO, don't hold it against them gang they aren't blacksmiths after all, you can't blame them for leading underprivileged existences.

All I do to anneal the things I was messing with was leave it in a section of the forge out of the main chamber but with enough leakage to be over 1,000f Yeah I even adjusted the partition bricks a little to make it so.

Here's something I was surprised to learn about molten glass, it's very viscous but the darned stuff is an astounding penetrant. Capillarity sucks it into virtually any void if it ISN'T completely open. The points on the negative space in the spread cross for example. I've tried a number of things to try containing it on the under side but it flows through ANY gap and spreads over the bottom side of the cross where it's laying on something. Getting the little points filled in the negative space of the cross on the other hand are so far not happening.

I purchased Red frit, same color as in this cross thinking if the corners are full to start I have it made in the  . . . .forge. Get it hot enough to flow and it's all over the place EXCEPT the corners. Getting it to slumping temp on the other hand has some really nice aspects it looks sort of like itty bitty bright red caviar just not in the corners.

Frosty The Lucky.

[bigb]

The glass will be in some sort of loose "crumbly" form from what I remembered she told me. She had a name for it but I forgot. She will pour in some of the glass and back it up on the bottom with some special paper. She has been doing kiln work for many years and makes beautiful things that actually sell, unlike my junk. 

Frosty yes this is for split crosses.

[ThomasPowers]

Frit?

[John B]

6 hours ago, Frosty said:

Annealing the glass is important but it's not as tricky as most folk think. Two points to consider when mixing glass and steel, they both have similar COE, not the same but close enough. The real buggaboo is thermal conductivity, the steel will cool much faster than glass. You keep them in an environment that cools everything at the same pace.

Another little trick is using the right kind of glass. Lamp work glass is a lot less sensitive to stresses and requires less annealing.

All I do to anneal the things I was messing with was leave it in a section of the forge out of the main chamber but with enough leakage to be over 1,000f Yeah I even adjusted the partition bricks a little to make it so.

Here's something I was surprised to learn about molten glass, it's very viscous but the darned stuff is an astounding penetrant. Capillarity sucks it into virtually any void if it ISN'T completely open. The points on the negative space in the spread cross for example. I've tried a number of things to try containing it on the under side but it flows through ANY gap and spreads over the bottom side of the cross where it's laying on something. Getting the little points filled in the negative space of the cross on the other hand are so far not happening.

I purchased Red frit, same color as in this cross thinking if the corners are full to start I have it made in the  . . . .forge. Get it hot enough to flow and it's all over the place EXCEPT the corners. Getting it to slumping temp on the other hand has some really nice aspects it looks sort of like itty bitty bright red caviar just not in the corners.

Frosty The Lucky.

The special paper mentioned by bigb is probably mica as it acts as a non stick surface for the molten glass, but if used on forged items there is the possibility of leakage on the underside due to the capillary action into any indentations, I have not used frit or powdered glass, mainly bits of broken coloured glass or glass marbles, and I have not used a gas forge to meld them in,   (what is meld ?: to (cause something to) combine with something else)

The first I made was in a microwave, details are on this site somewhere, and results would have been better if I had used a mica sheet backing for it, as it turned out, I had to grind/polish off some of the sharp bits left on the lower side when the items fused together, 

Other attempts have been succesfully done on a side blast forge, I say on rather than in, as I placed the cross onto a flat steel plate (3/8"), with the bit of glass or marble in the opening of the cross, The plate heats up, then the cross and then you can see the glass slump and flow, (slump is beter than melt as it leaves a jewel like finish at the front which acts as a lens if illuminated from the rear.) lift the plate off to one side of the hearth and allow all the lot to cool as you would when annealing/normalising steel.

Now comes the interesting bit, in practice, the glass slumps through and rests on the heating plate where it melts and flows, attaching itself to it and forming a bond between all 3 parts, glass, cross and support plate. This forms a potential shear line for the glass, keep your eye on this stage and remove from fire as soon as this occurs. It may take a couple of attempts to get it spot on, but the process is quite forgiving and you an always melt out the glass and repeat the process.

When they are at room temperature (or leave overnight) if you use a spannering motion between the cross and the plate, (sharp tap with a hammer on the cross, plate in vise) then  the glass usually shears off with a nice clean face on the rear of the cross, you can polish up if needed to remove any shards that may remain.

Have fun

[Frosty]

"Frit" is ground screened borosilicate glass sold by seive size. Think colored sand in various grits.

Polished stainless doesn't meld to glass well but if it scales up.   Maybe stainless steel foil?

Both "art glass" shops I've visited talked about release agents and non-stick paper but didn't have any. I know I haven't found anything melted glass won't stick to. . . so far. Neither of the shop keepers believed my idea would work, there is just too much about glass I don't know I'd have to anneal the pieces in an oven for a long LONG time. Even after I showed them a couple examples they didn't think it'd work.

Might be why they were out of release agents and paper eh?

Frosty The Lucky.

 

[ianinsa]

Ha Frosty, that paper/cloth is sold in the microwave kiln kits, I got one of those on my last trip to the USA, then gave a sample to my furnace supply guys and they got me some albeit somewhat thicker.

[ThomasPowers]

I haven't tried slumping but I have done some enamelling using my forge as the furnace and experimenting with grinding my own glass, (most had issues with spalling and adding borax did not help in my experiments; however a 1930's brake lens found in the spoil piles along the river worked a treat...modern stained glass was not suitable for my circa 1120  A.D. processes...)

[bigb]

Success! Here is the prototype after 2 kiln firings 

[Laertius]

well done!