heated glass

I need to make a heated (150 degrees F.) glass platen to use for blending
encaustic wax medium. The size if 20" X 24" and the glass could be from
1/4" - 1/2" thick and is supported fully from the underneath side. I've
tried to do this with hot air guns and heating lamps and busted the glass
(3/8" plate). Could I use a stick-on heating tape evenly spaced so the
temperature of the glass was uniform to relieve stresses and prevent
breakage ?? I sure would appreciate the groups advise on this project.

TIA,
Ed Angell

You need to get the glass up in the 1400 degree range give or take and
then you need to be able to anneal it down slowly. A hot air gun or
heating lamps are useless. find someone with a kiln and who is
knowledgeable in fusing with glass.

Andy
http://www.neoglassic.com

Ed Angell wrote:
I need to make a heated (150 degrees F.) glass platen to use for
blending
encaustic wax medium. The size if 20" X 24" and the glass could be
from
1/4" - 1/2" thick and is supported fully from the underneath side.
I've
tried to do this with hot air guns and heating lamps and busted the
glass
(3/8" plate). Could I use a stick-on heating tape evenly spaced so
the
temperature of the glass was uniform to relieve stresses and prevent
breakage ?? I sure would appreciate the groups advise on this
project.

TIA,
Ed Angell

i think you're just trying to heat up the glass to 150F so that the wax will
bend, and not trying to bend the glass itself?

glass doesn't like to have any part of it more than about 4 degrees
difference from any one place to another. you need to heat it very evenly to
accomplish this. think copier machines, which use light, or maybe a water
bath. you'd have to use a lot of strips to make it be evenly heated.

"Ed Angell" edangellatcomcastdotnet wrote in message
...
I need to make a heated (150 degrees F.) glass platen to use for blending
encaustic wax medium. The size if 20" X 24" and the glass could be from
1/4" - 1/2" thick and is supported fully from the underneath side. I've
tried to do this with hot air guns and heating lamps and busted the glass
(3/8" plate). Could I use a stick-on heating tape evenly spaced so the
temperature of the glass was uniform to relieve stresses and prevent
breakage ?? I sure would appreciate the groups advise on this project.

TIA,
Ed Angell

why not use a crock pot...they get well over 150 at medium set. or get one
with temp controls.


"Charles Spitzer" wrote in message
...
i think you're just trying to heat up the glass to 150F so that the wax
will
bend, and not trying to bend the glass itself?

glass doesn't like to have any part of it more than about 4 degrees
difference from any one place to another. you need to heat it very evenly
to
accomplish this. think copier machines, which use light, or maybe a water
bath. you'd have to use a lot of strips to make it be evenly heated.

"Ed Angell" edangellatcomcastdotnet wrote in message
...
I need to make a heated (150 degrees F.) glass platen to use for blending
encaustic wax medium. The size if 20" X 24" and the glass could be from
1/4" - 1/2" thick and is supported fully from the underneath side. I've
tried to do this with hot air guns and heating lamps and busted the
glass
(3/8" plate). Could I use a stick-on heating tape evenly spaced so the
temperature of the glass was uniform to relieve stresses and prevent
breakage ?? I sure would appreciate the groups advise on this project.

TIA,
Ed Angell

I think the heat of your problem is
"The size if 20" X 24" and the glass could be from
1/4" - 1/2" thick and is supported fully from the underneath side."
The glass should NOT be supported from the underside, which will keep it
cool and stressed across it's thickness.
I would recommend building a box (insulated somewhat) that holds the glass
at the rim, that is about 6" deep. In the box or at the bottom of the box,
put one of the following: a griddle, a hot plate, a wire heating element.
The advantage of the first is that it includes a heater control, but maybe
not that low. The dial would have to be protected from the heat. With the
latter two, you would need either a controller or try manual control with a
dimmer.
The goal is to evenly heat the glass from below until it gets to the
desired temp and hold it.
If you have a big enough kitchen oven, you could put the glass in the oven
and put it on warm, checking the temp with an oven or candy thermometer
until it steadies. I do this with plex and casting wax in a gas oven with
a long warm section and a low numbered reading of 200F
I have built boxes like the one above from sheetmetal and frax and from
insulating castable, but if you limit the temp to below 200F and the heat
source is well controlled, you can make the box of wood.

--
Mike Firth
Hot Glass Bits Furnace Working Website
http://users.ticnet.com/mikefirth/hotbit46.htm Latest notes

"Ed Angell" edangellatcomcastdotnet wrote in message
...
I need to make a heated (150 degrees F.) glass platen to use for blending
encaustic wax medium. The size if 20" X 24" and the glass could be from
1/4" - 1/2" thick and is supported fully from the underneath side. I've
tried to do this with hot air guns and heating lamps and busted the glass
(3/8" plate). Could I use a stick-on heating tape evenly spaced so the
temperature of the glass was uniform to relieve stresses and prevent
breakage ?? I sure would appreciate the groups advise on this project.

TIA,
Ed Angell

Why so thick?

The thicker the glass the more temprimental it becomes with heat. You would
be better off with as thin of sheet as possible.

Use Pyrex sheet glass. No window glass will hold up to thermal shock.
A heat gun won't phase Pyrex. Unless you stick the nose to one spot only and
don't move it. Pyrex's strain point is about 986F.

Randy Hansen
SC Glass Tech.
Scam Diego, Comi-fornia

Yes, but will the thin glass hold enough heat to allow the wax to lay flat,
etc.

--
Mike Firth
Hot Glass Bits Furnace Working Website
http://users.ticnet.com/mikefirth/hotbit46.htm Latest notes

"Randy H." wrote in message
news:UwKDd.79228$QR1.14072@fed1read04...


Why so thick?

The thicker the glass the more temprimental it becomes with heat. You
would be better off with as thin of sheet as possible.

Use Pyrex sheet glass. No window glass will hold up to thermal shock.
A heat gun won't phase Pyrex. Unless you stick the nose to one spot only
and don't move it. Pyrex's strain point is about 986F.

Randy Hansen
SC Glass Tech.
Scam Diego, Comi-fornia

Snip
TIA,
Ed Angell


I guess I should have laid out the whole process to be more clear.

I put a mixture of heated wax and pigment on the heated platen. I use a
heavy glass muller to combine the wax and pigment. The muller looks like a
large heavy paper weight with a vertical handle and a flat ground bottom.
You move the muller through the wax / pigment mixture in a figure 8 motion
until the pigment is thoroughly mixed into the wax. Ever so often, you need
to restore the tooth of the platen surface by grinding it using the muller
and a mixture of water and 400 grit Silicon Carbide. Unless you can keep
the wax mixture right at the melting point about 150-155 F., this process is
a bitch. I chose the heavy glass because of the weight of the muller and
the possibility of mechanical abuse when the wax sets up from time to time.

Would Pyrex sitting directly on a large hot plate work ?? If so, what
thickness would be the best ??

Thanks for suggestions,
Ed Angell

I would have suggested a hot plate or warming tray if I thought you could
get one as big as you want. And with what you are pushing on, I think you
need 1/2" or 3/8" glass, not window glass
I still think you will be much better off with a box to buffer the local
effects of whatever heating source you use, which could be a small warming
tray or a hot plate. I think that putting Pyrex directly on a hot plate
will create a wobbly work surface and depending on how you control the temp,
may still get too hot locally, even for Pyrex. If you moderate the voltage,
say with a dimmer or variac, it might work temp wise but still be wobley.
To be honest, you might be able, with a wooden box lined with thin
fiberglass insulation like used in ceiling panels, to get up to 150 with a
hundred watt light bulb or two and use a cheap light dimmer to control.
Since you are well below the boiling point of water, you could put a baking
pan in the box and pour boiling water in from a teapot but getting it out
and keeping the temp near 150 might be a drag (he said having softened pitch
for repousse)

--
Mike Firth
Hot Glass Bits Furnace Working Website
http://users.ticnet.com/mikefirth/hotbit46.htm Latest notes

"Ed Angell" edangellatcomcastdotnet wrote in message
...

Snip
TIA,
Ed Angell


I guess I should have laid out the whole process to be more clear.

I put a mixture of heated wax and pigment on the heated platen. I use a
heavy glass muller to combine the wax and pigment. The muller looks like
a
large heavy paper weight with a vertical handle and a flat ground bottom.
You move the muller through the wax / pigment mixture in a figure 8 motion
until the pigment is thoroughly mixed into the wax. Ever so often, you
need
to restore the tooth of the platen surface by grinding it using the muller
and a mixture of water and 400 grit Silicon Carbide. Unless you can keep
the wax mixture right at the melting point about 150-155 F., this process
is
a bitch. I chose the heavy glass because of the weight of the muller and
the possibility of mechanical abuse when the wax sets up from time to
time.

Would Pyrex sitting directly on a large hot plate work ?? If so, what
thickness would be the best ??

Thanks for suggestions,
Ed Angell

Mike Firth wrote:
I would have suggested a hot plate or warming tray if I thought you could
get one as big as you want. And with what you are pushing on, I think you
need 1/2" or 3/8" glass, not window glass
I still think you will be much better off with a box to buffer the local
effects of whatever heating source you use, which could be a small warming
tray or a hot plate. I think that putting Pyrex directly on a hot plate
will create a wobbly work surface and depending on how you control the temp,
may still get too hot locally, even for Pyrex. If you moderate the voltage,
say with a dimmer or variac, it might work temp wise but still be wobley.
To be honest, you might be able, with a wooden box lined with thin
fiberglass insulation like used in ceiling panels, to get up to 150 with a
hundred watt light bulb or two and use a cheap light dimmer to control.
Since you are well below the boiling point of water, you could put a baking
pan in the box and pour boiling water in from a teapot but getting it out
and keeping the temp near 150 might be a drag (he said having softened pitch
for repousse)



Perhaps you could try making a covered stand and "bowl" for the glass
plate. Make it open underneath and paint the backside of the glass
black with enamel paint, then suspend a 600W halogen shop-light about
a foot under it, pointing up at the black surface. This will get very
hot (and heat evenly over the full surface.) The lamp will need
ventilation though. If yer into electronics, there are several methods
for controlling the temperature accurately.


-- At it's heart, all a fractal is is a simple unbalanced dynamic,
like cos(1/z)*z. A fractal is unbalanced in such a way that it can
never be solved, and the longer it is "computed", the more complex it
becomes. It is literally a twist or gotcha, on infinity.