39 Ammonia Fuming: What is a fuming chamber?
Description
This article is from the Woodworking FAQ Collection 1, by multiple authors.
39 Ammonia Fuming: What is a fuming chamber?
Well, it's anything that can do the job, which means it's big enough to
contain the workpiece, but not excessively large and it must be readily and
completely sealed (including the bottom). I've made enclosures starting
with a lightweight frame made of 1x2 pine (twelve edges, open sides,
fastened by a handful of drywall screws). The box frame is completely
wrapped (around one axis) by a single sheet (if possible) of 4 or 6 mil
polyethylene. The wrap is started by stapling one edge of the sheeting to
an edge of the frame. The wrapping material initially is cut so that it
will extend several feet beyond each "open" end of the frame (think of
gift-wrapping a package). Duct tape is used to seal the only seam, which is
along the long axis (assuming you're not making a cube). If you ensure
there is adequate "extra" poly to extend well beyond each end, it can be
taped and/or rolled up and clamped tightly shut with numerous spring
clamps, heavy-duty clothes pins, etc.
Another approach would be to cut separate sheets of polyethylene and to
attach these (by stapling) to each side of the frame. Use duct tape to seal
each seam.
Introduce and arrange the workpiece (or its parts) through the opening of
the box; then when you are ready to close and quickly seal up the open
side, place (on the floor) inside one or two small dishes (p referrably,
widemouth jars) of ammonia solution . Remove the jar lid(s) and seal up the
opening. Even a large chamber should need no more than about a pint (total)
of solution. There is little harm in using too much solution--other than
the effort needed to reclaim the liquid for later use (or disposal).
For small pieces like a lamp base (clocks, boxes, etc.), it is possible for
the fuming enclosure to be merely a heavy-duty polyethylene yard (lawn)
bag. A plastic can (e.g., garbage can) could be used inside the bag to
provide some extra stability. To fume a 20"-high lamp base, I placed the
piece inside a plastic garbage can (probably 15 or 20 gallons) along with a
small jar of ammonia solution. I was then able to enclose the can within a
40 gallon lawn bag. After the jar of ammonia solution was opened, the top
of the bag was tightly rolled up and sealed with several spring clamps and
a couple of wooden battens to distribute the clamping force.
A well-sealed chamber is important because: (1) leakage could cause
discomfort in the vicinity (and possibly be a hazard to neighbors), and (2)
any major leaks could make it necessary to use very long fuming times (or
produce unpredictable effects).
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