Creating a mosaic with stone differs from other mosaic work mostly in the way that you cut the tesserae.
How I do it:
Disclaimer - I am not an expert, yet. I'm just telling you what works for me.
Most of the stone I use starts out as floor tiles. They run from 7/16" to 5/8" thick and are usually 12" x 12" in size. Sometimes I'll get the smaller ones, but there is more waste per piece with them since I trim off all the outer smooth-cut edges.
|Top to bottom: 3 shelves of cut stone tesserae, |
uncut stone tiles & slabs, bins of cut-up chunks
I cut the tile into manageable chunks - trying to get the chunks as rectangular as possible - with a hammer and hardie. I don't like manufactured edges to show in my mosaics, so I cut the stone to the point where the tessera has the "footprint" that I want and then I turn it sideways and cut it in half. This allows me to turn all the manufactured edges down and have only the hand-cut, irregular edges showing.
|Hammers & Hardies, left - steel hammer & hardie for cutting stone,|
right - carbide-tipped hamnmers and hardie for cutting glass
|Stone cutting process - note the progressively smaller cuts. The two |
small pieces on the top of the stack are ready for use in a mosaic.
You want to develop enough control that the force of the hammer-fall is transmitted just to the stone. There are two methods of swinging the hammer: to pivot at the elbow joint, or to pivot at the wrist. I try to isolate the pivot in my elbow joint. I find that it saves my wrist from the shock (important since I have some joint issues from earlier injuries). It also feels like I have more control and I don't fatigue so quickly.
When you're using a hammer and hardie it's important to avoid striking the hardie with the hammer as much as possible. It really dulls both the hardie and the hammer when it happens. I get the best cuts when I focus on making sure that I strike the stone exactly above where it rests on the hardie - so that the hammer tip is directly above the cutting edge of the hardie.
If I'm working with a very crumbly stone (soft limestone/sandstone) or stone that is prone to irregular cuts (heavily veined marble), I'll cut the tessarae using the hammer & hardie down to a certain size and then use my compound tile nippers or a CHEAP pair of glass tile nippers - not my Leponitts or my Montolits - to make the final cut. I have to admit that feels a bit like cheating... but I don't like wasting material and time.
I usually mix stone and glass in the mosaics. I like the rough stone and the smooth and shiny glass side-by-side. I also like the contrast between the subtle, muted colors of the stone and the more intense, pure colors of the glass.
|Dalle de verre and found glass|
The glass is usually dalle de verre with some smalti and the occasional weird found glass. The dalle de verre is cut using carbide-tipped hammer and the hardie. I also use a chipping hammer to distress the surface of any larger blocks of glass and also to create shards to use in the mosaics.
|Carbide-tipped hammers and hardie. Top: chipping hammer. Bottom: cutting hammer|
|This is what happens when your carbide hammer strikes the hardie unevenly.|
|The top of the smaller piece of dalle de verre has been distressed using the chipping hammer.|
I use mostly Wediboard for substrate. For the stone mosaics I use the 5/8" instead of the 1/2", mainly because of the finished weight. I have a local (well, within 150 miles) supplier for the wediboard, Cole Papers in Minneapolis. They don't list wediboard on their website, but they do sell it.
I use thinset mortar to adhere the stone and glass to the Wediboard. I've been using Mapei Keraset mortar, mixed with a 1:1 mixture of water and Mapei Keraply. I'd use Laticrete products, but I can purchase the Mapei products locally.
I color the mortar with Gamblin dry pigments or Sheffield Tints-All. Lately I've been mostly using the Gamblin but I stay away from the cadmium, chromium and cobalt pigments. I don't have a safe ventilation system for using them.