Heating up glass with Resistance wire

"Dave" wrote in
:


wrote in message
ups.com...
I am looking for resistance wire to heat up a piece of glass
250x300x4mm about 10° Celsius above room temperature. I've made some

....
As pictured in the diagram - 240mm of wire every 10mm for 290mm =
240x29 + 10x29 = ~7,300mm. That's 7.3m of resistance wire. Assuming
room temperature is 20°, the wire will temperature will need to be
~35°, to keep the glass at just under 30°.

The wire will be attached to one side of the glass surface using
self-adhesive clear plastic wrapper (similar to those used to wrap
books).

1. Are these calculations/assumptions correct?
2. What kind of wire (thickness) should I be looking for?
3. What will my power consumption be (will 12V @ 1A be enough)?

The general idea seems ok, but I wonder about heat losses and
acceptable temperature variation. If the losses are significant, than
the wire spacing of 10mm for 4mm thick glass sounds a bit high - glass
is not a good conductor of heat. One approach might be to use a piece
of printed circuit board (unetched), and place a continuous copper
plane next to the glass, with heating elements attached to the other
side (nichrome wire is good). The thin copper sheet will spread the
heat to give a more uniform temperature. Based on experience with
heaters for telescopes, 12W will not be enough unless the losses are
absolutely minimal.

Dave

Why try to bond wire to glass?

Paint or silkscreen resistive paint in a grid or other pattern like a
auto's rear window defroster.
You get better thermal transfer,it's far simpler.
Bond connnecting wires with silver conductive epoxy.


--
Jim Yanik
jyanik
at
kua.net

This sounds like another attempt to make an impasto plate. Buy a warming
tray with a glass plate and foil heating on the back. The wire to do this
will have to be real thin.

--
Mike Firth
Hot Glass Bits Furnace Working Website
http://users.ticnet.com/mikefirth/hotbit47.htm Latest notes

"Rich Grise" wrote in message
news
On Fri, 29 Jul 2005 11:55:01 -0700, sergeroz wrote:

I am looking for resistance wire to heat up a piece of glass
250x300x4mm about 10° Celsius above room temperature. I've made some
plans on how to do this, however I need some more guidance, especially
choosing and obtaining correct resistance wire.

Electricity will be supplied @ 12V DC @ 1A, or 5V DC @ 500mA if
possible.

See this diagram: http://img236.imageshack.us/img236/907/glass0zn.png
for proposed/designed layout.

As pictured in the diagram - 240mm of wire every 10mm for 290mm =
240x29 + 10x29 = ~7,300mm. That's 7.3m of resistance wire. Assuming
room temperature is 20°, the wire will temperature will need to be
~35°, to keep the glass at just under 30°.

The wire will be attached to one side of the glass surface using
self-adhesive clear plastic wrapper (similar to those used to wrap
books).

1. Are these calculations/assumptions correct?
2. What kind of wire (thickness) should I be looking for?
3. What will my power consumption be (will 12V @ 1A be enough)?

I'll be very thankful for any advice on this matter.

Go to the department store and get a hotplate or toaster-oven.

Good Luck!
Rich