11 replies to this topic

[Mumbles]

This is an off shoot of the Barium Chlorate thread. I didn't want to take it too far off topic. Below is a post from a gentleman in the US that did a lot of work commercially on the resourcinol bound comets, and really started the whole revival in the amateur community.



From lightnpyro on rec.pyro 3-17-07

You might want to try a comet mix that has been used for years in the
US consumer fireworks market, bound with resorsinal (spelling?) resin
(Borden RS-216) and catalyzed with paraformaldehyde (Borden RB-9).
Many, many thousands of these have been made and in spite of their
containing coarse titanium, the pumps show no noticable wear. They
were machined from solid bearing bronze and are still in service
after
15 years.

Red comet, with tail: %
Potassium perchlorate - 43
Strontium carbonate - 14
Saran 506 --------------14
Magnalium 50/50, -200 mesh - 10.5
Red gum ----------------3.5
Charcoal ----------------7
*Titanium, sponge PLUS 30 mesh - 7

*It is important to sift the titanium to remove the minus 30 mesh
material, as the finer size particles will tear up your pumps.

The mix is dampened with the following binder solution, based on
TOTAL
BATCH weight:
Resorsinal resin - 8%, that is thinned down with 4% methanol.
To the above mix, add:
Paraformaldehyde - 1%
(Mix well with an egg beater and add to comet mix. Knead well and run
the damp mix through a 1/4" screen a couple of times.
Press comets in the normal fashion. You will have about eight hours
before the mix hardens. It will warm up a bit but this is normal as
the binder sets up. Many tons of damp comets were placed in rather
hot
drying trailers but we never had a problem. No priming is needed. We
made comets up to 2" diameter and 2.5" tall.I think the same mix
would
work for 2.5" comets.
For green, substitute the strontium carbonate with:
Barium carbonate - 7
Bariun nitrate - 7 (a bit of boric acid might help with the green
version)
We also made a yellow using cryolite but I can't find any notes on
it.
A violet comet was made by replacing most of the strontium carbonate
with black cupric oxide. (9% CuO to 5% SrCo3?)
If you want the (dry) comets to be harder still, they can be briefly
dipped in NC/acetone solution and dried.

An example of binder/comet mix ratios:
Comet mix - 10 KG
Resin - 800 grams
Methanol - 400 grams
Paraformaldehyde -100 grams

I would like to hear from those that actually get off their butt and
try these out.

These mixes worked very well for us......
Your actual mileage may vary........
For outdoor use only....
Not a food product.......

[pyrotechnist]

I remember the british fireworks industry heading into the resin based direction especially Brocks Fireworks so seems to have been around for a long while. Wouldn't a NC based mix do something similar to this? I find resins a tad bit expensive to use on my stars or comets etc but I do see a lot of uses for it.

[Mumbles]

It depends what you want to use it for. If you're making stars, yes it is way too pricy. It really comes into it's own in regard to large comets. Large comets can dry (cure) in a matter of hours instead of months. Even NC, red gum, and other strictly solvent based things still have relatively lengthy drying times due to films and solvent retention effects. There is also strength issues. I just don't think NC or red gum have the strength required for these big comets, and are simlarly priced to the resins used.

[cooperman435]

Mumbles you quote the ratio of resin to hardener as 8:1 but dont mention if the 8 is before or after the thinning by adding the 4% methanol?

Also the Resorcinol resin I sell quotes a 5:1 ratio so may be worth checking as some suppliers may differ?

[Mumbles]

It's 8% before thinning. For a 100g batch it would be 8g of resin, 4g of alcohol, and 1g of hardener. I honestly don't know if he originally followed the instructions on the package or not. The people I've conversed with about this have simply followed the directions as written.

[pyrotrev]

Mumbles you quote the ratio of resin to hardener as 8:1 but dont mention if the 8 is before or after the thinning by adding the 4% methanol?

Also the Resorcinol resin I sell quotes a 5:1 ratio so may be worth checking as some suppliers may differ?

Yes Phill, different resins have different ratios. I guess it's a function of the resin chemistry, how concentrated the resin is (some types contain some water to make it easier to mix/pour) and whether the hardener is a liquid or solid. I 've used it a lot to make comets of all sizes and love it

[Vic]

Could these two part resins be used for cruciform crossettes or the shot hole types?

[Mumbles]

I don't see why not. As I am told, it is about the same consistency as normally wetted comet composition. It doesn't start getting really sticky or warm for several hours. I was actually thinking about sending a message to the guy I know with a lot of experience with this stuff. It might be a good way to make spider comets because they normally take so long to dry.

[cooperman435]

Ive used it for them and found it far easier than dextrin bound comps.

Once the mix has the resin added it is still a free flowing powder but turns into a solid puck under pressure very fast so it doesnt stick to tooling and can be removed from a crosette pump easilly

[dave]

Ive used it for them and found it far easier than dextrin bound comps.

Once the mix has the resin added it is still a free flowing powder but turns into a solid puck under pressure very fast so it doesnt stick to tooling and can be removed from a crosette pump easilly

phil ,
what is a typical general usage level in a star / comet composition.
it would seem to be quite low if you say that the final mix is still a"free flowing powder" ?

dave321

[cooperman435]

A typical comet Ive made would contain

100g rough milled BP (30 minutes milling tops)
30g Mg granules (around 16#)
5g resin
1g hardner

I would mix the dry ingredients, mix the resin with hardner and then add to the dry components and mix with a spoon till completely distributed. This will take some time as its not like wetting with water.

Adding water to the resin can help though makes quick usage less likely, acetone will help disperse it though it doesnt mix well with the resin which could be a good thing as it evaporates quickly, it should be allowed to evaporate though before the comet is pressed, Any of the alcohols can also be used though they are slower to evaporate.

some comps need 10g of resin per 100g of comp (with 2g of hardener) like charcoal dependant ones as they are so fluffy but experiments are needed.

Even with the incompatibility of the resin and MG these comets can be made and fired almost straight away and usually last for 3 days without problems for me. Mg is the only incompatability I know of.

[dave]

A typical comet Ive made would contain

100g rough milled BP (30 minutes milling tops)
30g Mg granules (around 16#)
5g resin
1g hardner

I would mix the dry ingredients, mix the resin with hardner and then add to the dry components and mix with a spoon till completely distributed. This will take some time as its not like wetting with water.

Adding water to the resin can help though makes quick usage less likely, acetone will help disperse it though it doesnt mix well with the resin which could be a good thing as it evaporates quickly, it should be allowed to evaporate though before the comet is pressed, Any of the alcohols can also be used though they are slower to evaporate.

some comps need 10g of resin per 100g of comp (with 2g of hardener) like charcoal dependant ones as they are so fluffy but experiments are needed.

Even with the incompatibility of the resin and MG these comets can be made and fired almost straight away and usually last for 3 days without problems for me. Mg is the only incompatability I know of.

phil,
thanks for that ball park figure

dave321