Precipitin zones

Doug Stand dougstand at
Mon Mar 6 00:48:07 EST 1995

Viewing boxes, using a small box (usually metal) with a small fluorescent
offset from a glass window on the box top, can provide an indirect light
The bottom indside of the box (under the window area) should be painted a
flat black.  A magnifier of 2-4x can be suspended or moved over the agar
when it is placed on the box window with the light on.  The light, shining
indirectly, will tend to highlight the precipitin line.  The flat black
immediately under will give a contrast.  The magnifier will help to
enhance the
show (a hand-held magnifier can work).  Other techniques I've used or
of:  1. allow more time for reaction (72 hours gives clearer lines than
      2. put reacted plates in a 6-10 degree C refrigerator overnight,
then re-read
      3. Try varying well depths &/or spacing, assuming ag/ab conc is
      4. some people have used weak acids or dyes - I never had to try
      5. or you can give up and move to ELISA or maybe nephelometry

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