Soft and crumbly core for stars?

[Sulphurstan]

I tried out a new star which has a nice white effect, but which is very crumbly after drying.

KP + fine Al flaky (Al bronze) + Al flitter flakes (up to 0,650 mm) + red gum + dextrin.

Dextrin is about 4 %.

 

The composition was wetted with alcohol water 50-50 (dext and red gum activated).

 

Cutted as 9 mm cube, even perfectly dry, I can crunch them between thumb and index finger 😦

 

So Im thinking on putting a THICK layer of prime, patiently rolled on to given them strenght to withstand the burst in the shell.... 3, 4 even 5 mm of prime.

 

Question will that work, or does the explosion will shatter them all because of this soft core ? (The concept of hollow charges, which explodes etc....😱

Should I better try another binder? ( i Have parlon, nc lacquer, just the basics)

 

Thanx in advance for any idea.

[Carbon796]

You should have picked just one, alcohol OR water binding. Neither one activated property ( they where both inhibited ) because of the 50/50 split.

 

If they are easily crushed you might try screening and re-wetting them with an appropriate solvet and re-cutting them.

 

Parlon is a chlorine donner - that can be used as a binder in some comps.

Red gum is a fuel - that can be used as a binder in some comps.

Edited October 9, 2017 by Carbon796

[Mumbles]

I've generally been unimpressed by the binding capabilities of red gum.

 

I agree with Carbon on both the cause and the solution, you would be better off crushing and rewetting them. Flake aluminums with stearic acid or other fatty coatings can be hard to wet at times. What I'd suggest is using a thin wheat paste instead of water to bind the stars (ca. 10:1 water to wheat paste). This is in addition to the dextrin in the composition. Even if you don't have instant wheat paste around it can be made from flour and water, which I'm happy to detail if you're unfamiliar with the process. The wheat paste helps to provide some wet strength to the stars when cutting, and seems to help bind the stars a little better. It doesn't always do the trick, and a splash of alcohol can help to cut the surface tension. By splash I'm talking an unmeasured amount, probably less than 5% total.

[OldMarine]

I've been berated by Mike Swisher more than a couple of times for trying to use something other than dextrin as the binder when the only reason the dex is there is to be the binder. Don't make me drag him over here!

[Sulphurstan]

Mumbles, yep, agreed, red gum is a weak binder.

I like the idea of wheat paste.

I'll stay on dextrin, and try the way explained, because, yes, my big Al flakes are stearin coated...

[Mumbles]

I find it most useful with comps containing fair amounts of bright flake, or other fine flake aluminums. I treat it as almost mandatory in most instances. Mass for mass they generally seem to have a lot more surface area, and thus generally a lot more stearin. For me, this makes it more resistant to water wetting and general binding. For coarse Al you can kind of take it or leave it sometimes, or at least it has less of a direct impact. I do think it tends to work a little like CMC or other things like that. It just keeps stuff in suspension a little better being more viscous. I do still use it frequently actually in these cases though. I use coarse Al in things like comets and streamers most often, and the extra binder never hurts.