On Dec 30, 2:11*am, Stealth Pilot
wrote:


you mention glue.
how do you make that?
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How you make it depends of what you're trying to glue together.

A good general purpose glue is made from raw hides. This can take a
pretty strong nose.

Go to one of the big Chain Stores that carries Pet supplies. Buy some
pigs ears or dried 'chewables' of rawhide.

Try cutting the rawhide or dried ears into smaller pieces. Depending
on how they were prepared, their size can be as large as 8x10 inches.
For making glue you want the size to be more on the order of 1/4 x
1/4" or in the form of strings. Soak the pieces in water until they
are fully saturated then begin adding heat. To maintain control of
the temperature you'll need to use a double boiler.

If you've never made hide glue, start by BUYING SOME, so you'll know
what it looks like. It is made from rawhide -- the residue of making
leather -- or from hooves and horns. Properly made, the stuff looks
like honey. In use, it may be thinned and heated.

Rawhide itself is rather handy stuff. When saturated with water it
can be stretched but will try to shrink back to its original size
unless restrained. You can make molds of things you wish to protect,
such as some of your precision tools. Soaking the dried rawhide in a
light oil will prevent it from absorbing water and losing it's shape.

For homebuilders the most useful glue is Casein. This is made from
the protein in MILK. Run your milk through a cream separator more
than once, or allow it to stand, giving the cream time to separate.
When making milkglue you want to be damn sure that you do NOT get any
cream in the mix. If you live in an area that does not provide real
milk, visit your local grocery store and see if they carry 'fat-free'
or 'skim' milk.

Starting with skim milk, add an acid such as vinegar to cause the milk
to 'turn'. Stir the milk to ensure the acid reaches all of the milk.
Allow it to stand for about half an hour then pour off the liquid (ie,
the whey) then whisk the curds into a uniform paste and neutralize
them using bicarbonate of soda dissolved in water. Heat this mix in a
double boiler to reduce it to the consistency of heavy cream. If you
are not familiar with this consistency go BUY some heavy cream... or
allow some real ice cream to melt. The basic test is to take it up a
teaspoon at a time and allow it to pour back into the container.
'Heavy Cream' is the point at which it pours back as a single stream
rather than as a series of drops.

The next step is to make sure you have neutralized the acid. The best
way to do this is with Litmus paper, purchased at the drug store or on-
line. If that is not available to you, you can do the test with a
STRONG mixture of bicarbonate of soda in warm water. Add this to
your mix ONE DROP AT A TIME whilst looking for it to generate any
bubbles. If the mix is still acidic you will have to add more
neutralizer, stirring it in good and repeating your tests. The
problem here is that you are trying to achieve a NEUTRAL mix, one that
is neither acidic nor base. The tests make it easy to DETECT acidity
but not the opposite, unless you are using Litmus papers, so you want
to very careful that you do not end up with a mix that contains too
much bicarbonate of Soda because the soda will precipitate out as
crystals within the glue line, reducing its strength.

If you glue is too thick you may dilute it with water; if too thin you
may heat it to drive off some of the water. When you have achieved
what you believe is your best mix, you must test it using the standard
FTC shear-strength test. That is,a coupon two inches wide by four
inches long, with the adhesive applied to a 2x2 area. The adhesive is
applied to both faces and clamped with approximately 70 pounds of
pressure, all this while maintaining a gluing temperature of about 70
degrees on the Fahrenheit scale. The test-coupon is sheared at the
glue-line by clamping the free end in a vise and striking the other
free end with a three pound hammer, using enough force to cause the
sample to fail at the glue line.

Examination of the failure should show that the WOOD failed over at
least 80% of the glued area.

Casein glue is stronger than most of the softwoods used in aircraft
fabrication. Unfortunately, casein glue is subject to biological
attack by bacteria and fungi. For that reason it is important to seal
any glue-line with varnish or paint as quickly as practical, and to
include inspection of that sealing surface, for any aircraft in
service. In a similar vein it is important that you do not allow any
glue to become contaminated before it can be used.

-Bob

-PS -- One of the more important uses of rawhide is 'corners.' (!)
That is, on tool kits and small pieces of luggage, or the cases for
such things as VOM's, binoculars and so forth. It's a fairly simply
chore to make a corner of solid aluminum, or of hardwood well sealed
with varnish, over which you may stretch a piece of saturated rawhide,
tacked or clamped to the back of the form until the rawhide is fully
hardened. It is then trimmed to the required shape and attached using
stitching, glue or rivets.

And of course, we use rawhide for mallets :-) Often times we need a
mallet having a particular shape and the only way to get one is to
sacrifice a new mallet, sawing the rawhide to the desired corner &
curve. But if we have a supply of rawhide (strip is handiest for
this) we can literally 'roll our own,' producing a tool that is far
superior to making the head our of lignum vitae or whatever. - rsh