Ok, third time replying might be the charm so....
I'm a metalsmith and often galvanic etch copper (20 or 22 gauge) bigger than my iron (6"x4"). I use the toner transfer method and have had some success using a laminator and an electric pancake griddle.
The laminator is used to get a light adhesion of the toner to the metal and to prevent bubbles forming when I iron.
I use the pancake griddle to heat soak my metal and then apply the iron to burnish and add more heat for the transfer.
tips:
- set the pancake griddle at 300 or 250 and the iron on the cotton setting.
- use a paper towel between the griddle and the metal so it doesn't slip around.
- use the iron to burnish the toner on to the metal I hold the metal with a piece of wood doweling
- don't get it too hot or things will get slippery and the toner will smear. :-(
- run the metal and resist pattern through the laminator many times to get things to stick. It still doesn't stick enough for my etching which is why I added the iron and pancake griddle
- The laminator I use was recommended by pcbfx a couple of years ago. They have a new recommendation now: http://www.pcbfx.com/main_site/pages/start_here/laminator_info.html
And here is some interesting tidbits on temperatures culled from various places on the internet:
printer fuser temperatures: 200 °C (392 °F)
laminator temperatures 5mil thick (one side) 225 to 240 F
iron temperatures (vary by manufacture but some guidelines are:
Linen: 230 °C (445 °F)
Triacetate: 200 °C (390 °F)
Cotton: 204 °C (400 °F)
Viscose: 190 °C (375 °F)
Wool/Polyster/Silk: 148 °C (300 °F)
Cheers,
Heather.