Like many fly tyers, I usually use acetone (lacquer thinners) to thin my head cement, but when I used it to thin Dave's Flexament, the flexament turned a horrible opaque colour instead of the usual clear. Did the "precipitate" in the lacquer thinner cause the flexament to go opaque?
Sort- of... the precipitate is caused by the solvent (acetone) and is the flexament going out of solution. A "real life" example is Koolaid (a powderized drink mix for those who may not know)... I don't know about you, but when a kid on Scout trips, we would try to stick every crumb of the powdered drink-mix into the smallest volume of water possible. In other words, we'd pour a small cup of water then try to mix into it a 'full' cup of the powdered drink mix. Well, if we kept it up and kept adding the drink mix, we'd end up with a "glop" of wet powdery gunk at the bottom of the container. While the reason for the precipitation isn't quite the same, the concept of precipitation (going out of solution and making a 'glop') is identical. 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). 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. 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. The argument against its use, as I understand it, is two-fold: First, some hypothesize that fish can smell it. Second, others claim that it is a cover-up for a poorly tied fly, where it is used in place of whip-finishes. Without stating my own preference TOO loudly, what is your opinion? Of course, these same people against the 'smell' of dried cement also soak their flies in a garlic and vienna-sausage-oil mix overnight... again, I'll let you guess my opinion on THAT one... ;) Just my 2 cents... off to work now... Pete
