Mumbles Posted July 24, 2016 Posted July 24, 2016 A couple of friends of mine also have had issues with willow formulas, specifically the Shimizu composition. It wasn't necessarily a getting lit issue, as much as it was a staying lit issue. Shimizu expressly describes willow shells a poka shells, which are designed to be burst relatively softly Willow is an effect that absolutely relies upon atmospheric oxygen for the effect and falling through the air so that slag being blown off the surface. My friend was under the impression that if breaking too hard, like a warimono or typical chrysanthemum, that the stars could more easily be extinguishged or surface be shed before lighting the underlying composition. Adding more priming may helped more by allowing the stars to slow a bit more than actually providing any more heat/fire, which makes sense given your preference for light pasting and heavy boosting. You can also just add a few extra parts nitrate to help it sustain combustion a little better too.
ExplosiveCoek Posted July 25, 2016 Posted July 25, 2016 Lloyd, would the migration be a phenomena happening during drying or already during the rolling of the star?I always rol charcoal based stars 'quite' wet to prevent any bumps and to realize uniform growing of the stars. Might be the difference that I rolled the stars last layer in an overload of loose powder this time. Normally I just let them pick up the last layer of prime, roll a bit more and dump them out of the roller onto the drying screens. Could be that there was formed a fire proof surface due do this indeed. Even more so as all my stars had more or less the same phenomena, and I all rolled them in the same way. Mumbles, I used even more flash in the shell's I shot last time. Also, if I would decrease on burst power it would be more like a horsetail effect. The breaks really weren't that hard. I also didn't at too much extra priming. All the stars already had 1 mm meal priming, and I only rewetted the stars and added 2-3 extra increments to create the rough/powdery surface.I was indeed thinking about increasing the KNO3 content a bit, but that is also to get a bushier tail.
lloyd Posted July 25, 2016 Posted July 25, 2016 Coek,The migration is caused by a combination of "too wet" and "too long". Let's face it, the Japanese use the Toro method, and that's just about as wet as it gets... but then they dump on quite a generous amount of dry comp to be absorbed by the Toro coating. Although you need to get the stars quite wet to prevent the "raspberries", you should not roll them for long after the last application of water, and should then quickly put on as much final coat as they will take, plus a little more. The finished stars should end up nearly dry to the touch, and dusty. If you pound them in the roller while very wet, the binder will migrate preferentially to the surface. Mumbles's comment about adding a bit more nitrate for really hard-breaking shells is sound, too. I don't personally have any willows that won't ignite from a hard flash break, but I've heard of problems others have had. LLoyd
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