mesh & exposure questions...

[Southtown Press]

Had a few questions -- didn't find quite what I was looking for in the forums...

1. Can anyone recommend the best screen mesh count for printing on wood?

what about on canvas?

2. I understand a metal halide grow lamp and a piece of glass makes a good compression-style exposure system -- and a halogen work lamp will also do the trick...

Will that halogen light still burn decent enough stencils? Would the extra money spent on the metal halide light provide substantially better/stronger results?

Or would the improvement be primarily a matter of shorter exposure times?

Thanks for any help...

~L

[squeegeethree]

Depends on what your how rough the canvas and wood are. Id start with as low as a 76 mesh and build up the surface until you can print with a 195 mesh.

[ohdanielsan]

yeah, definitely depends on the wood. a friend of mine is doing some prints on wood with a 230 mesh screen, but the wood is pretty smooth. also, halogen work lights should work fine. i have a 1500 watt light that i got for around $50 and it burns fine. metal halide is going to cost about 3-4x more, but if you have the cash go for it. you'll get faster burn times since it has a higher UV output than halogen.

[Andymac]

we use 200 up to 305 on wood, but for it to work at all the wood must be smooth and should be filled/coated/sanded, otherwise the print ink pulls up the grain. if it is rough, it will print rough - you can't print in a depression or a crack.

the time will depend on the intensity of the lamp. sometimes the UV intensity is not so apparent between halogen and MH - bulbs are all different in the spectral output, and its hard to find data on the wavelength of the light - tells you the UV range in nanometers, the best being 330-440 or 'actinic' (blue)
Visible light is much higher in the scale - Lumins is only brightness.

[squeegeethree]

we use 200 up to 305 on wood, but for it to work at all the wood must be smooth and should be filled/coated/sanded, otherwise the print ink pulls up the grain. if it is rough, it will print rough - you can't print in a depression or a crack.

I just printed a halftone job on salvaged construction yard plywood and it turned out perfect cracks and all. It was a full bleed on a full 4'x8' sheet too. The key is a course mesh, an ink that doesn't dry too quickly, and a course dot. Otherwise Andy's is right, the key is smoothness.

I posted all my info of that in another thread. You should do a search 'cause I'm gonna start eating and drinking now.