Melting Boro

[jane clifton]

I do fused glass as well as lampworking and we have a process called "pot Melt" which is where you put scraps of glass color mixed with a lot of clear in a flower pot and let it melt and drop out the hole to produce all kinds of really cool designs. Well, after dumping my knock off jar numerous times, I thought, hey, this would make a cool pot melt since most of it was clear.
Well, I put it in my kiln and when the cycle was over and I anxiously opened the lid, I found that the glass had only particially melted. So I thought I must not of let it soak long enough or gone hot enough. So I restarted it and put the soak in at 2 hours at 1700 degrees and still nothing.
Does anyone know what the melting point of Boro is? Surely its not more than 1700 degrees!!!

I figure if I can get it fluid at the torch, than it can't be that hot!!!

Thanks,
Jane

[somberbear]

i know its soft at that point.... but it takes a long long long long time to slump into a mass.....

the man that knows the numbers is marcel and his boro hot shop...

peace
rob

[Firekist]

an oxygen propane torch should be able to achieve a flame temp up to 5000 degrees.. at least in theory. edit.. that's kelvin, not F.. anyway..

the "working" temp of simax is listed as 2300 degrees.. and i'd guess that'd get you closer to your goal than 1700.

z--seth

[Steve Sizelove]

I had the pleasure of seeing the Kimble factory in New Jersey a couple of years ago. Their furnaces were massive - around 200,000 lb capacity and the size of semi trailers. My friends and I got a complete tour of the control room and even got to look into a few peep holes in the KG-33 furnace.

While in the control room, we asked about melting temps. The operator showed us some of the readings from the various thermocouples in the glass. They run a spectrum of temps to create a convection current for complete mixing of the batch/cullet combo. My memory is a little fuzzy, but I do remember that in the middle of the furnace it was a little over 2700 degrees F. I think the hottest spot was about 3200, but I'm not sure. The glass at the bell where the tube was being pulled was about 2300. Hot!!!

From talking with some of the boro color manufacturers, I get the idea that their melts are a little lower (not working with batch) - around 2300. Maybe Abe from Presion Color/Northstar will chime in and give more specific numbers.

I think most of the people using ceramic flower pots to do kiln casting are using lead crystal or some other soft high COE glass. 1200-1400 F will get that moving pretty well.

[ShttrdSpctrm]

the warning sticker on my Aim 1210 says toturn off all controls if interior temp reaches 2381 F. Can your kiln take that much heat, would be the question.

[smutboy420]

Boro is pretty stiff So it don't droop as easy as soft glass when at the softing point. It can divitrify and scuss up pretty bad to if its not heated fast enought.

[UmaJulz]

One of my kilns is rated to 2250... if I ever wanted to melt a pile of boro bits, I guess I could.

[jane clifton]

Thanks so much guys, I had no idea that it had to get that hot!I never thought the torch got that hot!!! Thank you for the lesson, I have a greater appreciation for the torch now~~

Jane

[Greymatter Glass]

From what i've seen casting boro is just about impossible.

Charles Bray is the only artists name that comes to my mind.... he's cast some really large boro pieces, but they were pretty simple. large but simple.

For the kind of flow you need the glass well past the liquidous stage and in full melt mode. From batch you'd need probably in excess of 3600, and from cullet probably at least 3000.

If you want to make Vitreographs you could probably do that at around 2800 if you were to tease the glass out the hole to get the flow started.

Also, as stated, phase separation and devitrification are serious problems with boro, MUCH more so than with soft glasses, so work hot, work fast, cool fast, and then anneal, don't let the glass sit at one temp too long.

-Doug

[HumanLathe]

2200 is good 2300 is better. pouring and fusing boro should be maybe 3000 but that is really hot boro and you have to have some bad ass elements to be doing that shit let alone a bad ass furnace. Boro hot shop anyone? To get the color glass hot enough to pull into rods some start as high as 2300 and some lower, but to pour it seems like 3000 would be fine. ITs not really the pouring where you run into trouble its the need to rapidly cool and then anneal that is hard I know some have fused the piece then blow huge fans on the surface to try and stop the devit forming. I haven't seen anything that has turned out acceptable yet.

[jazz]

an oxygen propane torch should be able to achieve a flame temp up to 5000 degrees.. at least in theory. edit.. that's kelvin, not F.. anyway..
z--seth

oxy-propane flame 5000 kelvin???
that would be around 8540 deg F... contemporary lamp working says oxy-propane flame temp is 5300 deg F....

[andrew brown]

We just plugged in "big bertha" and started some boro fusing tests last week.. So far we have done 5 firings with major success and many notes...weve tried all kinds of test , dichro prep, multiple fusing, casting, flameworking, and more all with success.. Without a release boro will stick to most things, but there are some safe surfaces..
1750 is giving a solid tack fuse, 1800 will make plates out of 1" rods, and 1800 for 20 minutes will fully fuse/slump pieces. After 20 min at 1800 you can pull a fused sheet of rods out of the kiln and flamework....Devit is a problem, but not as bad as you would think. Also re flameworking pieces can be tricky without skimming off a thin layer.. Pieces that come out of the kiln and into the flame directly dont dont seem to have any devit at all...
still working on tests, more to come, with pictures..
andrew

[Cosmo]

I fused some boro a few months ago. By accident. Well, I guess technically it's "slumped" and not "fused", but I have no doubt that if I had put separate pieces on top of each other they would have become one piece.

I put some marbles in with some pieces a friend was making. The relay stuck in a new Paragon F-120 and this is what I ended up with.

http://www.soleiletlune.com/gallery/fused%20glass%20002.jpg

Not sure the temperature that the kiln reached, but it was running wide open. There is a little devit on one of the big marbles (second from right), but everything else is nice and smooth. This devit is really just some large wrinkles. One more interesting note - the white color on the marble on the left is the Chinese amber. For some reason it turned opaque white.

So, yeah, it's definitely possible. I have never tried to do it on purpose, so I don't really have any tips. But you can do it.

[newmexicomagma]

rock on andrew cant wait to see what ur coming up with now. ive accidently slumped some pieces in my old kiln but not now since i have a digi. i thought they looked pretty cool.

[jane clifton]

So how do you pull a rod at 1800 out of the kiln and flamework!!!! ouch!
I would imagine that the same kiln wash we use in fusing would work as a release for boro as well.
If your temps are true than what everyone else has said is true, if you graduate the temps to what would make it porous. Regular glass fuses at around 1500 depending on the thickness and becomes liquid at around 1700 depending on the kiln. So that would lead you to beleive that Boro could become liquid at aroung 2000 if held for a long time.
Interesting

Jane

[jane clifton]

You said you did casting as well, what temperature did you do that at and out of curiousity, what kind of schedule did you use? Did you cool quickly or slowly?

Thanks
Jane

[smutboy420]

Isn't the key to avoiding the divit to take it to temp quickly and cool it down to the stiffing point quickly. So it don't have time to form the dibit?

[mer]

in 2003 glass alchemy, the eugene glass school and skutt teamed up to work on the "boro fusing project". all of the info from this work can be found in the dec/jan 2003/2004 issue of glassline magazine (Volume17#4). according to this article fusing boro is possible at a temp between 2000 and 2100 degrees for 20 minutes. apparently a fast ramp up and down is most successful and was aided by the use of specially made fast ramping skutt kilns. by ramping from 2000 to 1300 as fast as possible they were able to avoid phase seperation that was otherwise problematic. the most successful surface to fuse on was found to be a kaiser board or a mix of kiln wash and plaster of paris. the article also talks about the results of different color rod and frit tests but there is too much info to copy here.

[Swampy]

To help eleviate devit whilst fusing float glass, previously I've sprayed a light coat of 'Spray A' over the top surface then fusing it.

Spray A, as far as I can understand, is a fine crystal frit suspended in a carrier liquid. You can airbrush it on or use a plant sprayer.

I've rescued heavily divitrified work by sandblasting off the scum then using spray A and re-fusing but only holding at full fuse for 5 minutes.

I haven't used it on boro, someone would have to experiment and share with us what they find. I am curious. I don't have the facility right now; still awaiting blanket for current kiln build.

Incompatibility wasn't an issue, either using it on either float (coe ~65) or BullsEye (coe 90).

Let us know what happens if anyone tries it okay.

edited to add a polite request;
and if you do find out, please don't write in big long paragraphs cos it does my fucking head in trying to read it. Yes you, MM!!! :-)

[Orrza]

Jane, I don't understand why....
Pot melting is beautiful, I have seen some plates made with it.
but boro is :
1. So much more expensive
2. takes so much more heat and resorces (electricity etc...)
3. has less colours avalable
4. takes a load bunch of time to melt

Why not make it with soft glass?
(If you say you make special rods with it, or a plate roll and blow into something else like a pipe or a jar I undestand)

p.s.
you know what... forget it, I just answered myself :LOL:
COOL!!
:)

[jane clifton]

Orrza,
Actually I was just looking for a way to use all the glass out of my knock off jar!!!

Jane

(I hate to throw anything away)