MAKING YOUR OWN GEL BOXES
John H McDonald
mcdonald at strauss.udel.edu
Thu Feb 23 22:11:40 EST 1995
In article <9502231545.aa07644 at etsuodt.etsu.edu>,
GORDON BETTS <betts at ORION.ETSU.EDU> wrote:
>We are sitting here discussing the construction of gel boxes for molecular
>biology labs. We are thinking of building our own for undergrad teaching labs.
>Some questions we came up with:
>1). What glue to use for construction? Apparently regular silicon has acetic
>acid in it.
The shop where you buy plastic should have the appropriate cement for
acrylic or polycarbonate plastic. Some of these cements are just a
solvent which dissolves the plastic. The advantages of these are that,
if you have a good joint, you can assemble the joint, then apply the
cement to the edge and it will run in by capillary action. The resulting
joint can be as strong as the plastic itself. Other cements are thicker,
because they contain both the solvent and some dissolved plastic. These
cements have to be applied to the joint before it is assembled, but
because they can fill small gaps, they may be more forgiving.
>2). What are the ideal dimensions?
Whatever seems ideal to you, that's part of the beauty of building your own.
>3). Where do you obtain the platinum wire and what dimension to use?
Scientific supply companies such as VWR and Fisher sell it. Get the
thinnest they sell, it will be cheaper, and plenty thick enough to carry
the small amounts of electricity you'll be using. You can get the banana
plugs and sockets at Radio Shack; if your physics department has a
stockroom, they'll probably have them too.
>4). How do you bend plexiglass?
Remove the protective paper and put it in an oven, on a cookie sheet, at
300 F (150 C) for a few minutes. It should be floppy enough to bend it
over a wooden form. You can buy a strip heater designed just for this
purpose, but they're pretty expensive. I'm told that if you're real
careful, you can heat the plastic with a propane torch held just the
right distance away until it is soft enough to bend.
>5). What is the ideal tool to use for cutting plexiglass? Table saw, coping
>saw, chain saw (just kidding)?
A band saw is best, a table saw will work. Be sure to wear eye
protection, little chips will go flying everywhere.
>6). Are there different plexiglasses?
Plexiglas is one brand of acrylic plastic; I think it's also what's
called perspex in other countries. I doubt there's much difference
between brands that will make a difference for gel boxes. You might also
consider polycarbonate plastic, since it's tougher and resists shattering
better (it's what bulletproof windows are made of). Make sure you get the
correct cement, I think a different cement is needed for polycarbonate.
When you shop around for plastic (most glass shops sell it, as do many
hardware stores), ask if they sell scraps. They often have a big pile of
scraps, big enough to make gel boxes from, that they'll sell for
cheaper than custom-cut pieces. For the combs, delrin works well. You
may have to call around a bit to find some, though.
John H. McDonald
Department of Biology
University of Delaware
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