It appears that you use a birch lid to seal the box when not fuming. Both Iodine and Bromine will degrade wood very quickly. You may want to line the lid’s inner surface with a thin piece of teflon or glass. If you use glass, be sure to grind the top edges of the inner box.
The inner box holding the Iodine or Bromine appears to be glass sealed at the edges with caulk. Both those chemicals will cause the caulk to fail (particularly quick stuff) and the box to come apart. See if you can find a one-piece glass baking dish that will fit your box so that there are no seams to get compromised.
But please don’t tale my suggestions the wrong way – you have built a terrific system here, and I want you to be able to use it a long time without failure.
Now, lets see you buff those big plates…
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