Full Version: Granite vs Marble ? Settings etc.
From: Larry B (PALMETTO) [#11]
21 Apr 2007
To: MIKEY (JADEPUTTERS) [#2] 21 Apr 2007
Mikey;
Thanks, proof's in the results. Your work looks great! I'll try this setting and see what my laser gives me.
EDITED: 21 Apr 2007 by PALMETTO
From: Mikey (MIKE2449) [#12]
23 Apr 2007
To: Larry B (PALMETTO) [#11] 23 Apr 2007
Larry:
Just checking to see if you have worked out the diff between the stones. Granite is an igneous rock (from the earth's core). Generally it is far harder than marble. Marble is a metamorphic rock, originally from the earths surface, pushed below the surface cooked for a couple hundred million years and quarried by man. Both are quarried in different manners. The Italians are the best marble quarriers in the world, Finland is (in my opinion) the world leader for granite. Both stones come out in blocks, weather they are wire cut or drilled and blasted. These blocks vary in size, however, they are about 5' x 5' x 9'. If they are used for tiles (usually 1cm thick) they are processed by a "tile line" machine. This type of machinery takes the block, slices it up, cuts to size, gauges stone and polishes all in one big line. The sizes are typically 12"x12" or 18" x 18". The Italians have really made this process state of the art. If one wants larger pieces, usually they are 2cm, 3cm or 5cm thick. This process is like the old bakery bread cutters. The block is placed under a large frame with spring steel blades. Water with abrasive is applied as the blades are lowered onto the block and slid back and forth just like the old bread cutters. It takes about 8 hours to cut through a block of marble. It takes just under 8 days to cut a block of granite in this method. They have just developed high tensioned diamond wire saws (reciprocal) that has cut this time dramatically I'm told.
If you haven't found out by now, every stone is slightly different. Absolute black granite can and does have a different surface appearance. Sometimes the "fleck" is very, very small--other times it is larger. I have found that the granite with the smallest fleck gives the best image. Lasersketch has come across a very hard absolute black marble. This particular stone has almost a white background when lasered. I use full power with this stone about 35% speed and always 600 dpi. For regular absolute black marble and absolute black granite
I reverse things a bit. I have found that 15% power and 20% speed give me the best image on granite. Also, I use 300 dpi on black granite. I use these settings on absolute black marble as well, only with 600 dpi. A trick I learned here is to use Armorall before you laser. Just apply and wipe off right before you laser the stone. I don't know why this works but am doing some research now. Normally with black marbles (like Negro Marquina) the final polish uses tin oxide and oxalic acid to shine. (We used to use felt pads with lead).
Hope this isn't boring everyone and I'll end it here. Hope this is of help.
Mike
From: Stunt Engraver (DGL) [#13]
23 Apr 2007
To: Mikey (MIKE2449) [#12] 23 Apr 2007
Very informative.
Thank you,
From: Larry B (PALMETTO) [#14]
23 Apr 2007
To: Mikey (MIKE2449) [#12] 24 Apr 2007
From: Mikey (MIKE2449) [#15]
24 Apr 2007
To: Larry B (PALMETTO) [#14] 25 Apr 2007
Larry:
Use every sq in of the stone. Below is a pic of a piece of stone I used to test on--it is black absolute and has since been completely filled.
Good luck.
Mike
From: Larry B (PALMETTO) [#16]
25 Apr 2007
To: Mikey (MIKE2449) [#15] 25 Apr 2007
Mike:
I ran one of these big pieces of granite this morning. I put a large photo that I made of some boats on it, 10" x 22". I used a setting of 100 speed-44 power, took 26 minutes. It turned out beautifully. I ran the whole thing, photo, text and all at 300dpi. This setting was recommended by a guy in the Sawmill Creek forum that has an Epilog 40w, same as mine. It worked great. Thanks for all your help and advice, I appreciate it. I'll post a photo when I can get one made.
EDITED: 25 Apr 2007 by PALMETTO