goldsilverpro said:
I see no reason to melt in the hood, anyway. Make it a chemical hood with enough heat resistance to use a hotplate.
I see many benefits from having a fume hood that is fire proof, and absolutely none to having one that is not. Frankly, to suggest one be built of wood is reckless and shows a serious disregard for the safety of others.
The reasons are wide and varied. Having worked with a fire proof hood for more than fifteen years, I can't imagine not having the ability.
Here's some things to consider:
A fume hood is not a luxury, it is a necessity if a person is serious about refining. Otherwise you're always at the mercy of weather and other issues that may be better in control of when you can operate. Further, you can operate at greater speed, so your time is much better spent. That may not be an issue if one is simply enjoying playing with a few items, but if the refining operation grows, spending hours on a a ten minute operation is no longer an option.
Think of handling acids----without the need to wear a respirator. You can dispense all acids with no worries. A good and proper hood will create a negative atmosphere, always pulling fresh air past you. Your wife will love it for peeling onions!
Fact is, it's not a bad idea to do all torch work in a fume hood so you are not exposed to gasses from melting. There are toxic elements one can encounter on a regular basis (think silver solder with cadmium, for an example). It's not solely about melting-----there are many reasons to work in a hood.
A hood that is not fireproof is an open invitation to an eventual fire, particularly if it is of wooden construction and has been adequately exposed to nitric acid. A hood that is fire proof is the best insurance you can buy to protect you and your family.
Assuming an individual decides to serve the jewelry industry, aside from refining items large enough to be inquarted, everything must be incinerated prior to any refining operations. Closing the door on jewelry waste is simply a stupid idea. The effort to extract an ounce of gold from such waste is, perhaps, only 1/100th the amount of effort expended in stripping pins and other low grade wastes.
Work towards a fume hood with this in mind:
Building a hood that is not fire proof will cause a person to eventually build a second hood of sorts, for incineration. As I've stated previously, incineration is very much a part of refining and should be practiced on a regular basis. The outcome is far better, often with the benefit of solutions that will filter easily, whereas they were previously difficult. By making a hood fireproof, a second hood is not required, so there is a space savings for those that are working in limited quarters.
Harold