braddsn Posted January 24, 2015 Share Posted January 24, 2015 I know some of this might be nitpicking, but I am getting ready to bulk up my star inventory for my 4th of July build, and I want to get this right... I know that as a rule of thumb, 30% of star weight is a good amount of prime to use. When calculating the 30%, should I be weighing the stars wet right after I roll them? Or weighing the dry comp, then calculating the amount of prime? Again, I know this is a small detail, but the weight of the freshly rolled wet stars is significantly heavier than the dry comp before rolling. And also, (again nitpicking), when using the KP hot prime system (KP prime first, with layer of scratch mix bp+mgal+DE+silicon), do I just 50/50 these primes, or use like 80% KP prime with 20% bp layer? I have about 80% success with stars lighting so far, but there are times when I will have blind stars, and I believe it is due to lack of prime. Up to this point, I have not been weighing my prime.. I have just been guessing and throwing it on. I want to start being more precise now, and adding prime by weight. Thanks for the input. Link to comment Share on other sites More sharing options...
FlaMtnBkr Posted January 24, 2015 Share Posted January 24, 2015 Since water is an unknown variable due to people rolling different I would think it's by dry weight. I don't really go by weight but by how thick the layer of prime is. 1-1.5 mm thick seems about right for most things. If using one prime go thicker and if multiple go thinner until you get to that thickness. If you weigh them before and after you will get the appropriate weight increase but I don't normally do that and eyeball it. You need to make sure that the prime you use is hot enough to light your star. And not all prime lights easy so some prime needs a layer of BP to act as a prime for the prime. It doesn't hurt to finish everything in BP. Link to comment Share on other sites More sharing options...
braddsn Posted January 24, 2015 Author Share Posted January 24, 2015 (edited) Ok... I think what confuses me is, I have heard a lot of guys say "just add 1-2 mm of prime". Problem is, there is really no way to accurately judge that.. unless you are constantly sprinkling a little prime on, then taking a star out and measuring with a micrometer. I know what you are saying about eyeing it, but at least for me, it's hard to judge size down to the mm when I have a 2kg batch of stars rolling. Up to this point I have been eyeing it, but that finally came back and bit me in the a$$. I fired several shells the other night, and a few of the shells blew blind stars. I could tell by watching closely, that the prime was lighting, but going out too fast.. therefore the stars were still traveling too fast when the comp lit.. blowing them out. I guess what I am trying to do here is nail down a failproof method.. i.e. by weight.. taking all of the guesswork out. I agree with your thoughts.. it makes the most sense that you would weigh dry comp and dry prime. Like you said.. the water is too unpredictable from person to person. I am going to weigh my dry comp, then weigh out 30% dry prime. Thanks FlaMtnBkr. Edited January 24, 2015 by braddsn Link to comment Share on other sites More sharing options...
FlaMtnBkr Posted January 24, 2015 Share Posted January 24, 2015 I think a lot of people only increase a star diameter so much at one time, let dry, and add more. So eyeball it, let dry a day, and then cut one open to check thickness if worried. If a bit thin add some more. You can weigh the prime but that will be an approximation as well. Denser comp will make a thinner layer and bigger stars will have a thinner layer for a given weight of prime. Even if you use a percentage of weight for the prime you should still cut one open and check how thick the layer is. Link to comment Share on other sites More sharing options...
MrB Posted January 24, 2015 Share Posted January 24, 2015 Cant tell for anyone else, but i screen my stars, to make them the same size. Adding prime once they are all the same size leaves me with a good idea of how large they all are, and how much they need to grow to have a sufficient layer of prime. (Most the time) i do roll one composition at the time, and dry the stars after that.B! Link to comment Share on other sites More sharing options...
Recommended Posts