How to clean a crucible or melting dish.

The chemical resistance of the Nevamar (sp?) is quite impressive, and would likely serve you quite well for a chemical hood, although I believe they recommend it not be applied to a cement type substrate.

The only other issue I'd have is that it won't resist the type of heat required to incinerate----so you'd likely have to consider a second unit for that purpose. It also may not be an issue if you have no plans of running wastes from a jeweler's bench. The incineration process for buffing lint and furnace filters used in their polishing machines is quite a long one, so what ever you'd use would be required to resist excessive heat for some time.

My second hood was entirely made of asbestos, but it was open bottomed, and sat on a piece of 3/8" Transite. Under the Transite was a sheet of 3/4" plywood. I used a three burner hot plate, fired by natural gas. The top of the hot plate was 6" from the Transite (Susan is using an identical hot plate for cooking while we're building our house).. I regularly noticed the slight smell of burning wood when I'd incinerate. Only when we moved to the castle did I discover the source. Directly under the hot plate burners there were circles that had charred almost completely through the plywood. That provided the input I need for construction of my final hood and rest. I used a base of 1¼" asbestos board in place of the 3/8" Transite, and that was supported by additional pieces of the same material, set on edge, 6" tall, so the dead air space under the 1¼" board was great enough to eliminate any chance of combustion. That system worked perfectly. I had two drawers under the hood (below the dead air space), in which I kept all the little tools and aids that I used in melting and handling hot items, so it worked out very well.

Expect to go through a couple of renditions of what ever you design, each one better than the last----for each time you're likely to miss something. It was my third hood that turned out quite well, but even then I missed the size of the fresh air supply. They were too small, so the hood was quite turbulent unless it was operated without the front cover.

Work towards a hood that doesn't have to be dismantled to clean it. A couple of removable covers may be all that need be required. If you make the cleaning operation too difficult, you won't do it. I dreaded doing my hood, and it wasn't all that hard to do. It was one hell of a messy job, for I always ended up with gold stains. I got over my ill feelings when I'd recover the values!

Here's a tip for you to consider. By now you know that gold chloride is photo sensitive, and doesn't wash off. Silver nitrate is, as well. I routinely worked with a few layers of newspaper spread around my counter area. About every second or third day, I'd remove the top one and incinerate it, to recover any values that may have been splashed, plus to keep the paper looking as good as old newspaper can be expected to look. If, by chance, you happen to have a spill, the paper will absorb the spill, making recovery of values a lot easier. It is for that reason that I kept a few layers of papers instead of just a sheet.

Harold

Steve,The chemical resistance of the Nevamar (sp?) is quite impressive, and would likely serve you quite well for a chemical hood, although I believe they recommend it not be applied to a cement type substrate.The only other issue I'd have is that it won't resist the type of heat required to incinerate----so you'd likely have to consider a second unit for that purpose. It also may not be an issue if you have no plans of running wastes from a jeweler's bench. The incineration process for buffing lint and furnace filters used in their polishing machines is quite a long one, so what ever you'd use would be required to resist excessive heat for some time.My second hood was entirely made of asbestos, but it was open bottomed, and sat on a piece of 3/8" Transite. Under the Transite was a sheet of 3/4" plywood. I used a three burner hot plate, fired by natural gas. The top of the hot plate was 6" from the Transite (Susan is using an identical hot plate for cooking while we're building our house).. I regularly noticed the slight smell of burning wood when I'd incinerate. Only when we moved to the castle did I discover the source. Directly under the hot plate burners there were circles that had charred almost completely through the plywood. That provided the input I need for construction of my final hood and rest. I used a base of 1¼" asbestos board in place of the 3/8" Transite, and that was supported by additional pieces of the same material, set on edge, 6" tall, so the dead air space under the 1¼" board was great enough to eliminate any chance of combustion. That system worked perfectly. I had two drawers under the hood (below the dead air space), in which I kept all the little tools and aids that I used in melting and handling hot items, so it worked out very well.Expect to go through a couple of renditions of what ever you design, each one better than the last----for each time you're likely to miss something. It was my third hood that turned out quite well, but even then I missed the size of the fresh air supply. They were too small, so the hood was quite turbulent unless it was operated without the front cover.Work towards a hood that doesn't have to be dismantled to clean it. A couple of removable covers may be all that need be required. If you make the cleaning operation too difficult, you won't do it. I dreaded doing my hood, and it wasn't all that hard to do. It was one hell of a messy job, for I always ended up with gold stains. I got over my ill feelings when I'd recover the values!Here's a tip for you to consider. By now you know that gold chloride is photo sensitive, and doesn't wash off. Silver nitrate is, as well. I routinely worked with a few layers of newspaper spread around my counter area. About every second or third day, I'd remove the top one and incinerate it, to recover any values that may have been splashed, plus to keep the paper looking as good as old newspaper can be expected to look. If, by chance, you happen to have a spill, the paper will absorb the spill, making recovery of values a lot easier. It is for that reason that I kept a few layers of papers instead of just a sheet.Harold