Physics suppliers sell a latex suspension that looks like milk; its purpose is
to replace the real milk that we used to use in the 'old days' to scatter light
through water.  A more concentrated solution might be suitable for you.  since
it is water based, you'll be able to add more water to replace that lost through
evaporation.

I know that Edmund Scientific used to sell the stuff.

Pasco and Educational Technologies are other possibilities.  Pasco tends to deal
for the high end of the market, though, so perhaps they won't be as suitable for
an item like this.

Jim Mallerdino wrote:
>
> Hello,
>
> I am working on an exhibit showing milk being processed through a plant.
>
> It is a small unit maybe 8' long x 6' height.  We are using an air pump
> to bubble through a liquid which simulates milk (Plexi Polish).  Texture
>
> and color are great. The liquid is enclosed in clear PVC tubing. The
> bubbling actually makes the liquid seem to be circulating through the
> system even though it is actually standing still.  My problem is the
> plexi polish evaporates quite rapidly, 2-1/2 gallons a week. The entire
> system has only 5 gallons total in it.  I believe that the plexi polish
> is alcohol based hence the evaporation. Also contributing to the
> evaporation is the amount of airflow needed to simulate circulation
> through the system. At the air release we have incorporated a Heppa
> filter and recovery reservoir. They are always completely dry.
> The system originally had a main tank from which we pumped and
> circulated the liquid through the pipes. However this was constantly
> overheating and leaking and difficult to maintain.
> Has anyone had any experience simulating milk? Would you happen to have
> any suggestions on a liquid or chemical formula which we could use with
> in our existing system?
> I know oil works really well as far as being non evaporative. However,
> it is not the right color and can't be dyed white to look like milk. We
> also tried machine tool/cutting fluid but as it sat overnight it left
> residue with in the pipes. Any help is greatly appreciated.
>
> Thanks,
>
> Jim Mallerdino
>
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Alistair Kwan                                        -
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