Priming Stars

[usatrapper]

Ok, I know this may be a bit of a "newbie" question but all the star comp's ive been working with do not require a prime.. Now that I am working with more complex star comp's I am finding that most of them require a heavy prime.. Only problem is that I have do not know how to prime stars.. A step by step explanation on how to prime stars would be greatly appreciated.

[TheEskimo]

It depends what type of stars you're working with. AP and KCLO3 stars require a different prime than KP and KNO3 stars. AP stars require a prime with no nitrates in it. Chlorate requires a prime with no sulfur in it.

The basic procedure is to make your stars. Once they have dried for about 15 mins, they are placed in a star roller/bucket, and prime of your choice is poured onto them. They are shaken gently. Then you wet them w/your solvent of choice, and put on more prime, until you have about a 2mm thick layer of prime. They can now be dried.

You can also prime them once they are done drying. For this, you use the same procedure, but you must gently wet the stars w/solvent of choice before aplying the first layer of prime.

Some stars are hard to light w/only one layer of prime, and must use two different primes. The inner prime burns very hot--this means metals. The outer prime must ignite easily, and still be able to ignite the inner prime.

You must also have a binder in your prime.

Now go out, and look for the prime that suits your star comp--there are lots on the forum. Personally, I go for BP+10% metal, but I only work w/KNO3 or KP stars. If you are using Ap or KCLO3 stars, watch out for the incompatabilities present.

Admins--Perhaps a move to the newbie section for future reference?

Edited December 25, 2009 by TheEskimo

[usatrapper]

Wait.. I am using Simple White #1 which obviously has no chlorates in it.. Can I just make a BP slurry and dip them in it?

[TheEskimo]

By simple white #1, I take it that you are using:

KNO3--28

Sb2S3--6

S--8

Dex--1.5

In any case, make your stars. Then, take meal powder, and if you wish, add 5-10% metal powder (Al, MgAl, Si). Mist the stars with IPA/water solution, with a spray bottle on "mist" setting. Pour on the meal, and coat the stars by rolling/shaking gently. Mist again, and pour on more meal, and shake/roll gently. Repeat until the layer of prime is several mm thick. Let the prime dry. Your stars are done.

[Arthur]

Rolled stars; simply build the stars to a good size then throw prime comp onto them as they continue to roll they will gain a layer of prime on the outside.

 

Cut Stars; Dust the cutting board with prime, then roll out the comp over the prime adding prime as the comp spreads along the bench, Cut the stars and dust the upper surface and all the cuts with prime.

 

Pumped stars; roll each star in a dish of prime as you pump them, or let them dry then mist the outsides of the star with solvent and roll in prime.

 

Remember that stars primed with dry powder will LOOK dry long before they are! Try drying for a week for every millimetre diameter or drying in a warm place or a good dehumidifier

 

"Dry to constant weight" is a phrase from my lab days that is still very valid! If it's losing weight over the days then it's losing moisture -so keep drying a bit longer! The last bit of moisture has to migrate from the core of the star so it has a long way to migrate before it can evaporate.