Ask A Scientist© Chemistry Archive

 
name       Jason
status     other
age        30s

Question - One of my students has asked me about "exploding paint". I
can't seem to find any information as to how it is made, what it is made
of, and what it is used for. Can anyone give me some insight?
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I think I recall a substance that may fit the "exploding paint" concept. My
HS chemistry teacher made some up every year around the first of April.
(Because of costs, safety, disposal concerns, etc. you'll want to limit this
to small batches.) A solution of ammonium iodide can be "painted" onto
notebooks, bottoms of shoes, etc., and will make a popping sound as the
dried residue is compressed. Technically speaking, I think the
noise-forming rxn is an implosion rather than an explosion. The
chemical-supply houses sell the substance already prepared, but I think it
can be prepared from aqua ammonia and tincture of iodine. Due to the
ammonia odor, this should be done in an area with ample ventilation (good
fume hood if possible). Use an excess of ammonia to cover evaporative
losses. Older CRC Handbooks of Chemistry and Physics have specific gravity
tables for ammonia solutions to simplify determination of activity (much
easier than titration, just make sure that sample is adjusted to proper
temperature - tables may be found elsewhere also.) If you don't have
reagent-grade ammonia in your lab supply, you may be able to talk your local
farm supply depot out of some Ag-grade product {take your own HDPE or
coated-glass container with closure. Label bottle apropriately, and secure
MSDS from supplier or from internet} Do NOT use household ammonia because
the detergent blended in will sap some of your iodine activity, and it is
generally very weak. The iodine tincture (available from drug, discount,
and grocery stores,) will show the weight% of iodine present. The rest is
chemistry.
Tim Spry
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