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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 Boric acid – ————-1 *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% (It may be wise to add the boric acid, ground to a fine dust, to the binder solution as well. We never did but there is a small amount of water in the resin that might do some good.) 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 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
