granite is my bane

[James Jaragosky]

ok I officially do not like granite foe laser engraving photos.
So I was wondering if I could cover the granite with some kind of masking tape and raster off the parts that need to be engraved and then take it to my sand blast cabinet and hit it with glass bead at a low to medium pressure.
any suggestions on this are appreciated.
thanks jim j.

[James Stokes]

you can do that, But granite should be easy to engrave. What specific problems are you having?

[Ryan Sprole]

James,

You just want to etch the surface and not go too deep. Low resalution is best say 150 or 200 dpi. Are you using black granit and are you using photo grave to create your image? Also you need to use an inverted image.

Ryan

[Lee DeRaud]

And whatever power setting you're using, cut it in half and run a small test.

Then cut it in half again. :eek:

Trust me on this.

[Rodne Gold]

You will get fantastic results blasting it , better than laser engraving (which doesnt actually "engrave")
You will however lose a little resolution blasting.
We use the shiny silver sign vinyl which is polyester based as a resist. It's a devil to remove but you can attain really deep blasts.
What works ok , but is a little fiddly is paper based sign vinyl application tape (similar to masking tape). Problem with that is that its very easy to blast right thru so we use 2 layers.
Lasers just leach colour out of marble and granite so you often get variable results when lasering both as both are natural materials and no one piece is the same as another. Of course there is very little depth and almost no way to fill nicely (we often fill blasted stone with silver or gold rub n buff type waxes)
In essence there are 2 ways of laser engraving both marble and granite , low power high speed to leach colour and low speed high power to fracture the stone with a thermal shock (like glass) to get an engraving you can feel. However using the latter often "burns" the stone and gives less than satisfactory results.
When using a resist to blast the stone , one has to use grosser resolution settings cos the particles have got to impact the stone and thus the holes in the resist have to be big enough to allow blasting media to pass thru.
One of the problems when filling blasted stone is the fact that the stone is often porous and the waxes or fill can stain it.

[Bill Cunningham]

Rodne! What res. do you make your resist etch to get a decent photo in stone? This is something I have never tried. I just installed a blast cabinet a few weeks ago, but have been too darn busy this month to play with it! haven't even poured in the first load of grit yet..