pyrogenius007 Posted October 20, 2017 Share Posted October 20, 2017 Hi, I have made a batch of red and green stars, the red ones were made with Potassium Chlorate, Strontium Nitrate, Magnesium and PVC, when mixed with THF the pvc got dissolved and acted as a binder I cut them into stars and the result was good hard stars. The green stars were made with Barium Nitrate, pvc, pot.chlorate and magnesium, however, when I added THF the stars were very crumbly and did not hold as well as the red ones, moreover a large portion of it was left as powder, what could be the reason for this ? can anybody give me any advice/suggestions on this ? I also have shellac paste (the sort that is used in automobiles to stick gaskets) shellac powder is not available at the place I stay. Can the paste diluted with acetone be used as a binder ? I have seen many formulas where the proportion of shellac is given in weight, if shellac paste is used how to measure the right proportion?. Please guide me on this. I have seen several videos on shell pasting methods, I would like to try out the method in which one long strip is pasted from the fuse end to the bottom of the hemisphere and the next strip is short, starting from a little below the fuse and ending a little above the bottom with each strip overlapping the other. Does one complete round result in 2 layers ? Link to comment Share on other sites More sharing options...
AustralianPyromaniac Posted October 20, 2017 Share Posted October 20, 2017 I have no idea in regards to your final question mainly because I don't even understand what you're talking about but I might be able to help with the first two. To start, it might be useful to inform us exactly how much PVC the stars contain if not the whole formula so we can diagnose the problem. My hunch would be the green contains less PVC and thus didn't bind properly or you let the THF evaporate by not working fast enough. More relevant information almost always gets you a better answer here. Secondly, in relation to the 'shellac paste' the simplest way would just be to look up the MSDS, can we have the product name? Failing this, you could try and evaporate it and weigh it before and after. Consider, the product you have may not even be shellac at all but in fact, some synthetic resin marketed under the same name. Or, worse, it could have additives that make it incompatible with chlorate which is why I would steer clear. Just thinking out loud here. Regards, AP 1 Link to comment Share on other sites More sharing options...
pyrogenius007 Posted October 20, 2017 Author Share Posted October 20, 2017 Thanks AustralianPyromaniac for your reply, the formula for Green stars is Barium Nitrate 42, Potassium Chlorate 16, Magnesium 25, PVC 15 Lamp Black 2, the stars are called Metal Green stars. The shellac paste is a local brand and what you said about it being a synthetic product may be true. As for the THF evaporating quickly I followed the same method that I used for the Red stars i.e. adding the THF to the powder which was placed on a plastic carry bag sheet and I mixed and kneaded it immediately by folding the other half of the bag over the mixture, the same way that was done for the red stars, even while spreading this mixture on a sheet it was still damp, only after cutting the stars and letting them dry I noticed that they were crumbly. BTW I also have some CPVC glue which is used for fixing CPVC pipes, can this glue be diluted with acetone and used as a binder ? Sorry for the final question, I should have put it under shell pasting methods. Link to comment Share on other sites More sharing options...
Mumbles Posted October 20, 2017 Share Posted October 20, 2017 If I read it correctly, then yes that pasting method results in 2 layers for every complete time around the shell. As long as the strips overlaps each other by 1/2 their width at least. Link to comment Share on other sites More sharing options...
pyrogenius007 Posted October 21, 2017 Author Share Posted October 21, 2017 Thanks Mumbles for your reply, I will try this method on my next shell, the problem with the video I had seen was that it was in Russian or some other East European language which I could not understand. However I will give this a try and post you the result. Thanks. Link to comment Share on other sites More sharing options...
AustralianPyromaniac Posted October 21, 2017 Share Posted October 21, 2017 Looking at a few other comps that use PVC as a binder 15% seems on the low side although some comps do use ratios like that. I would say it was because the percentage simply wasn't high enough as most comps such as those seem to use 15% PVC and 5% Dextrin to bind. What was the red comp's formula that you made successfully? Regards, AP Link to comment Share on other sites More sharing options...
pyrogenius007 Posted October 21, 2017 Author Share Posted October 21, 2017 AustralianPyromaniac, thanks for the reply, this time I will increase the PVC content to 18%, the same which was used for the red stars. As for the composition of the red stars the original was Pot.Chlorate 30, Strontium Nitrate 20, Magnesium 30, PVC 18 and Lamp Black 2, however this colour was not very intense, more like pink. I was advised to reduce the Chlorate and replace it with Strontium, now I am using 20% Pot. Chlorate and 30% Strontium Nitrate and retaining the rest of the items as they are, this gives a more intense red colour. Regards, PG. Link to comment Share on other sites More sharing options...
pyrogenius007 Posted October 25, 2017 Author Share Posted October 25, 2017 AustralianPyromaniac, I increased the PVC content to 18% but this also resulted in crumbly stars. I then added about 3 to 4% of CPVC glue diluted with acetone to it, this acted as a good binder and after cutting and drying the stars they held firmly. I have primed them with a layer of homemade B.P and they were easy to ignite. Thanks for giving me your advice. Regards PG. Link to comment Share on other sites More sharing options...
AustralianPyromaniac Posted October 26, 2017 Share Posted October 26, 2017 No problems PG glad you got it working. Oh... and I like your new signature ;-) Regards, AP Link to comment Share on other sites More sharing options...
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