coogan1997 Posted December 12, 2015 Posted December 12, 2015 Earlier today I was going to cut a batch of Independence red. I am using PVC instead of parlon, so i decided to use the red gum as the binder. But I noticed pretty quickly that the wetted comp didn't seem to hold together at all. I considered using dextrin instead but considering how hygroscopic Strontium nitrate is, it might lead to some problems with the high humidity in puerto rico? Could dissolving the red gum in denatured alcohol before wetting the comp possibly help?
lloyd Posted December 12, 2015 Posted December 12, 2015 (edited) Coogan,You said nothing whatsoever about how you wetted it. With what? How long did you 'temper' it before using? You also said you chose red gum "as the binder". That automatically presumes using alcohol or acetone as the wetting fluid. Without one or the other of those, red gum isn't anything but a 'dry fuel'. Further, strontium nitrate, sufficiently pure, is not terribly hygroscopic. Drying in the sun should dry it adequately. If not, use a dehumidified drying chamber at about 100-degrees F. Tell us more.LLoyd Edited December 12, 2015 by lloyd
coogan1997 Posted December 12, 2015 Author Posted December 12, 2015 I used about 22% of denatured alcohol. I mixed the alcohol with the dry comp in a ziplock bag and kneaded it for about 5 minutes, then i waited about an hour or so
lloyd Posted December 13, 2015 Posted December 13, 2015 (edited) When you said it didn't hold together... under what circumstances? Are you pressing it? Rolling it? Trying to form a loaf and cutting it? It makes little sense that THAT much alcohol shouldn't properly dissolve red gum. On the other hand, the remaining question is "how much solvent, total?" If you didn't introduce enough to truly wet the comp, it may be that there just wasn't enough dissolution of the gum to work. BTW... in the presence of excessive solvent, red gum isn't 'sticky', it's slippery. So I guess there's also the possibility that you used too much solvent. It's always a good idea, when changing binder/solvent packages to "sneak up" on the wetting amount, lest you over-do it. Lloyd Edited December 13, 2015 by lloyd
coogan1997 Posted December 13, 2015 Author Posted December 13, 2015 Well, after I wetted it ( still inside the ziplock bag) i squished it into a ball. After making a ball, which was barely holding together, I put that ball between two wax paper sheets and made it a patty. I did try more solvent but it made the situation worse.
lloyd Posted December 13, 2015 Posted December 13, 2015 I did forget to ask, "how much red gum?" Anything less than about 6% probably wouldn't be a good binder, by itself. LLoyd
coogan1997 Posted December 13, 2015 Author Posted December 13, 2015 Independence red contains 11% red gum
Ubehage Posted December 13, 2015 Posted December 13, 2015 I have only little experience with this, while trying to make some very simple red gum-bound BP-stars. But little is not equal to nothing Red gum-bound compositions will usually be rather fragile, and crumble easily untill they are almost fully dried.It's easy to get tricked by this. The stars may appear dry, before they really are. And, if you are not pressing the stars, they might feel like some kind of puddy. And hence, break up even easier before they are dried.
lloyd Posted December 13, 2015 Posted December 13, 2015 and they take FOREVER to dry, because red gum and alcohol make a varnish-like liquid that skins over and protects itself as it dries. L
Mumbles Posted December 13, 2015 Posted December 13, 2015 The few times I made red gum bound stars and compositions I never had too much trouble with them drying. Then again, this is in comparison to shellac which is notorious for skinning over. Which of the independence red's did you use? There are several variations published. I agree with Ubehage. The few times I was making red gum bound stars, they had significantly less wet strength compared to most other binders. Pressing stars helps with this. It seems sticky but not strong. Also, are any of your chemicals coarse? Stars with coarser components tend to have a little less wet strength too.
coogan1997 Posted December 13, 2015 Author Posted December 13, 2015 (edited) Which of the independence red's did you use? There are several variations published. The one I'm using is:Strontium nitrate 53Mgal 19Parlon 17 ( I used pvc instead of parlon )red gum 11 All my chems were pretty fine except the strontium nitrate which a blade milled for about a minute. But i guess it wasn't fine enough because it felt gritty even thought it was a fine powder. Also, the wetted comp did consolidate into a ball but crumbles when squeezed. Edited December 13, 2015 by coogan1997
lloyd Posted December 13, 2015 Posted December 13, 2015 "Also, the wetted comp did consolidate into a ball but crumbles when squeezed." ---That, alone, is not an indication that it will not dry hard. There are several binder/solvent combinations that manifest that property when dampened, but still dry rock-hard. Lloyd
Twignberry Posted December 21, 2015 Posted December 21, 2015 Just a thought, I haven't bound any stars with redgum but I did notice solubility drops significantly with water %. I had some denatured (95%) ethanol that had been sitting over redgum for a few weeks so one can assume it was saturated. When water was dropped into the solution, a creamy precipitate formed. Were you using 22%/ weight comp of pure denatured ethanol or 22% volume of ethanol in water solution for wetting?
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