How to Build a Clean Box

Andy Piercy wrote: Andy, Basically, the purpose of the clean box is to ensure that the air you're working in is clean. The box should be made from something that won't turn readily into dust, for example, it should *not* be made of cardboard. Plastic works best. Also, the box should have at least one clear side. I used perspex for the sides and top and thick rigid PVC for the base. It's important for you to be able to see what you're working on. Third, it's important to get the box sealed up well, so use plenty of thick silicone sealant along the corners. And make real sure that the silicone is completely and thoroughly dry and set up before you use the clean box. It also couldn't hurt to join the corners on a miter. In mine, I use a false bottom that holds together with some bolts to make it easier to open and close the box, so I can get tools and items to be repaired in and out of the box. Fourth, it's a good idea to use an inert gas supply. For reasons of availability and price, the best choice might be nitrogen. Bottled nitrogen won't be completely clean, so an air filter is probably a good idea. Don't use a paper one, obviously. I use a glass allergen filter. And the gas should go through a regulator. If it comes out too quickly, it could get supercooled, and that would not be fun. And don't forget to create a gas outlet with a one-way valve, to prevent outside air from getting in. If you don't put in an outlet, the gas will find its own outlet, and that won't be good. Obviously, it isn't possible to work in a completely sealed cube. You also need a place to put your hands into the box to actually *do* the work. The most reasonable method for doing this is to attach a pair of gloves to the box itself. Again, getting a good seal between the box and the glove is of paramount importance. Use a sealant material which has enough flexibility to do the job. Also, it would be a good idea to have a way of changing the gloves without tearing the box apart. I mounted my gloves to the box on opposite ends of the box so that I can get my hands to anywhere in the box. One thing I didn't think of until after I had built the box is that the positive pressure inside the box doesn't have to be very high, so you don't have to use gloves that are very rigid. I used pipefitters' gloves the first time, and I lost a lot of fine control. I suggest using something much thinner. Experiment! It's the easiest way to figure this stuff out. And let me know how it goes. I'd be interested to know. Good luck. Peace... Sridhar