Shellac instead of Red Gum

[Nitrato]

Hello.

Its pretty weird, but 'no matches were found' to the word "red gum". Of course, I must be doing something wrong, or Im just crazy.. So I started this thread.

 

Most star formulas I recall uses red gum, I tried many times to find a decent local supply of it, but without sucess. The artists houses only carry other gums (shellac, etc). There is also the online red gum from ebay, but is quite expensive.

 

Since I have plenty source of shellac powder, what the odds for substituting it for red gum?

Is there some problem regarding becoming acidic (like arabic gum)?

 

According to pyroguide, shellac powder have the average elemental composition C16H26O4. I tried to search a approximate formula for the red gum ( CAS 9000-20-8 ) but none msds I have seen have this info. So anyone knows what the best ratios I can use to substitute red gum by shellac, giving about the same result (the same reducing power)?

 

Are there also another good alternatives to red gum?

 

Thanks!

Edited April 6, 2012 by Nitrato

[Nitrato]

Hello.

I found some threads with a little more work.. Just searching for 'shellac' instead red gum gave me some interesting results:

http://www.amateurpyro.com/forums/topic/6155-shellac/page__p__78700__hl__shellac__fromsearch__1#entry78700

http://www.amateurpyro.com/forums/topic/6289-shellac-flakes/page__p__80845__hl__shellac__fromsearch__1#entry80845

http://www.amateurpyro.com/forums/topic/6921-why-not-always-using-shellac-with-chlorates/page__p__90976__hl__shellac__fromsearch__1#entry90976

 

These good info solved most of my questions. It seems chlorate based stars are better made with shellac than perchlorate. But Im still worried about stability of shellac solutions.. A online document, Handbook of Pharmaceuticals Excipients , I found claims a different elemental formula for shellac:

Elementary analysis reveals that shellac contains carbon,hydrogen, oxygen, and a negligible amount of ash. Orange shellac contains approx. 68%carbon, 9%hydrogen and 23%oxygen,and with a molecular weight of 1006 (bleached shellac is 949) the empirical formula for the average shellac molecule is C60H90O15 .Even with this relatively low molecular weight, shellac has excellent film-forming properties.

 

It also presents a somewhat handy solubility table for shellac:

 

SOLVENT SOLUBILITY @ 20°c

======================================

Alkalis--------------Soluble

Benzene--------------1 in 10

Ethanol--------------1 in 2

Ethanol (95%)--------1 in 1.2 (very slowly soluble)

Ether----------------1 in 8

Hexane---------------Pratically Insoluble

Propylene Glycol-----1 in 10

Water----------------Pratically Insoluble

 

Well thats it.. I will try make tomorrow some of these shellac star beauties and report people later.

Thanks.

[50AE]

The third thread you mentioned explains many things about both

[Nitrato]

Hello 50AE, thanks.

 

Right now I have two kinds of shellac, the first one is milled shellac from a pyro friend, and the second is hardware grade flakes, bought two years ago but still fine:

 

http://i242.photobucket.com/albums/ff176/tnitrato/pyro/Gomalaca-2tipos.jpg

 

Ive tried a modified version of veline blue, replacing the same amounts of shellac (in place of red gum) and PVC (in place of parlon), since I dont have these two components.

 

http://i242.photobucket.com/albums/ff176/tnitrato/pyro/stars/Veline%20blue%20modified/DSC01891.jpg

http://i242.photobucket.com/albums/ff176/tnitrato/pyro/stars/Veline%20blue%20modified/DSC01892.jpg

 

The prime was BP/dextrin/MgAl.

I dont have a video for its burning, but is somewhat slow but acceptable. Unfortunatelly my brief 5 days pyro-holidays ended and I moved to another city where I study, so I cant perform any new tests in next 2-3 weeks, but I will do and report later.

Well, blue/red chlorate-shellac stars will be the next business on free time, although Im a bit worried about my SrCO3 since it contains some strontium sulfide, that was revealed when I made some strontium nitrate from it.

[FlaMtnBkr]

Has anyone tried vinsol resin as a substitute? Don't hear much about it.

[Algenco]

as I recall, the use of Red Gum was the result of a search for a cheaper alternative to shellac

[Mumbles]

I had some vinsol but never really got a chance to try it out. I was told it is a direct 1:1 replacement for redgum, but works better with chlorates. I've never had a problem with RG and chlorates though. I bet it'd work as a replacement for rosin too. It certainly smells nice. It reminds me of fresh cut pine lumber (probably for a good reason).

[Potassiumchlorate]

I have the brighter pine-smelling type. Milled some of it recently. Shimizu states that the darker one is superior, though. Haven't tested it much, only in a blue Hardt composition.

[50AE]

Never tried it for colors, I only heard it's inferiour for colors than shellac and red gum. It's nasty to work with though, it's sticky at room temps.

[Mumbles]

It sounds like you get a different product over there than the stuff I've used. It was less sticky than shellac and used to be used almost exclusively (maybe still is) by several manufacturers in the US.

[Potassiumchlorate]

I do have some dark colophonium, the kind you use for violins. It's awfully expsnsive, though, about €10/30 grams. This seems waxy and probably can't be milled but must be scraped, like you scrape stearin from candles.

[Potassiumchlorate]

I'm still a bit undecided whether I should use shellac or red gum with barium chlorate in stars. 20mm shellac stars in a 6" are far too big, which I experienced on New Year's Eve. The stars were magnificent but burned much too long. Some of them even reached the ground.

 

Binding with shellac is a problem what the prime concerns: the shellac is brittle on the surface, so much of the prime falls off, if you roll an alcohol moist star in pinball prime, for instance. It might be better to bind with dextrin after all, except for when making Bengals.

 

Red gum doesn't seem to burn much faster with barium chlorate, btw. Potassium chlorate and red gum burns almost twice as fast as potassium chlorate and shellac. With ammonium perchlorate the difference is much less, and barium chlorate is much more sluggish than potassium chlorate.