On 16 Nov, 2006, at 12:20, Peter Gramp wrote:
Sort- of... the precipitate is caused by the solvent (acetone) and
is the flexament going out of solution.
[...]
To draw the parallel full circle, the Flexament (while not a
powder) would form a 'pseudo-powderized glop' in the liquid acetone
(again, while not the same cause for the precipitation, it is a
similar outcome).
Depends on the rate of addition of acetone. Normally, with a silicone
rubber being chased out of solution, you don't expect a 'powder'...
If I remember the MSDS (it's 6am, so I likely don't...), Dave's
flexament uses a 25/30/45 % mix of (I think mineral spirits, but
forget) to MEK (methyl-ethyl-ketone) to tolulene. While acetone is
often misnomered the 'universal solvent' in some chemical circles,
it truly isn't... Some things dissolve and/or dilute easily, others
don't dissolve at all.
COuld be, but the original bottles mentioned chlorinated solvents. It
still smells like there is at least some PCE in it...
There will be a test tomorrow, so I hope you took good notes ;)
To get this 'thread' back to fly- fishing (and away from the
chemistry), I wanted to open this 'can o' worms': A local debate
at the TU meeting has been whether to use head cement or not on flies.
No head cement. Justification: when tied correctly, no whip finish
needs head cement to stay put. Adding a cement head is one more
superfluous action. Now with flies that require a neat head for
looks, or for 'bucktail wing' flies, it is different. Also, when you
SUBSTITUTE cement (in the form of CA glue) for a whip finish, you
clearly need that cement (apply to thread BEFORE making the final
wraps).
The argument against its use, as I understand it, is two-fold:
First, some hypothesize that fish can smell it.
BS
Second, others claim that it is a cover-up for a poorly tied fly,
where it is used in place of whip-finishes.
Well, if you can't make a decent whip finish you're perfectly free to
augment it with cement. Why force people not to use cement when they
really DO need it? Once they progress to making a decent whip finish,
they'll eventually discover that they can dispense with the cement.
Henk
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| Dr. Henk J.M. Verhaar | e-mail:
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| Ecotoxicoloog en vliegbinder | tel: 035 656
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| NL-1244 PK Ankeveen | web: www.xs4all.nl/
~flyrod |
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