Treating Andamooka Colour Matrix
The No Acid Method
When you recieve your stone/s PLEASE look at them WET & IN DIRECT SUNLIGHT AS THIS WAS HOW THEY WERE PHOTOGRPHED. The treating penetration usally gets into the stones sbout 1/4 of an inch at best, this varies with induvidual stones due to various stones due to various matrix host rock deing different in hardness and porousity. With a lot of my material, I treat the larger size rough blocks first then clean a coupel of faces to expose the colours. Then I cut for the best colour flash etc. and treat again. OR you can just slice your stones and treat. Or slice and shape to your finished jewellery item then treat... or shape down already treated material and then treat again if you loose the black background from the treatment. What you need is an electric slow cooker a Crook Pot, they have internal heating element inside the base of the machine and a removabel ceramic bowl with lid. Cook on Keep Warm setting not High setting or you end up with Tofee! My machine holds about 3 litres of liquid. Pour about this amount of boiling water into the ceramic bowl and then add about 3 pounds of brown sugar and stir until you get a very saturated dissolved sugar solution, the more sugar the better really, as if your stones end up brown and not black just add more sugar and re-cook. I usally trow my stones in the cooker as I cut them in the morning. Take stones out, do not wipe any of the sugar off and you do not have to let them cool down. Wrap the stones individually in foil wrap.
Place the wrapped stones inside a cast iron container with lid and place this on top of lighter gas burner ring and fire bake for about 2 hours. It will smell a bit for the first ½ hour. " hour is optimal time for the camp oven size that I have. Mine mesures about 6 inches base internal diameter, to a 8 inches diameterat the lid rim and about 3 inches high siddes. Ater firing take the stones out. Allow about 1 hour to cool, open the foil packages and clean your cut face or where ever an a grinding stone wheel with water to expose the colours trough the finished black background. The actual firing carbonises the sugar in the stone turning it black. You know like a Black Opal.
Due to a lot of this material being porous, it is hard to polish out the small porous pits on the surface of your finished stone. A product called OPTICON can be used to seal the stone in conjuction with polishing and buff etc. Presoak as it says in desciption on product. you can reuse the mix. Pour it on a bottle. Or use a non-yellowing acrylic lacquer: an automotive aerosol product that comes in aerosol spray from the auto accesories shop at about 3-4 $ works great on most. Called TOP COAT CLEAR" deies very hard and can take a buff, etc.
Thanks to Stew
Ray Tollefsen of Cutters Table