Priming 1/4" Pumped Stars

[gizmothegecko]

Hey everyone,

I’m having trouble priming 1/4" pumped stars. My usual method is spraying them with water in a container, shaking them until they’re evenly wet, then transferring them to another container and adding the prime. This works, but it takes 3–4 cycles per layer, so with a step prime, I end up doing 6–8 cycles total. I need a thick prime because I’m going for a hard break.

I also tried dipping the stars in water using a metal strainer and then applying the prime. That works for some comps, but others get sticky and fall apart.

I’ve thought about rolling the prime on, but I’ve never rolled stars before and don’t have a roller. I've only used pumped or cut stars.

Does anyone have an alternative method for priming? I’m open to learning to roll prime, but I’d rather not build or buy a star roller if I can avoid it.

Any suggestions would be greatly appreciated—thanks!

[Carbon796]

Using a dissolved binder solution. Picks up more prime per layer. Than a plain water spray. But it also can cause more clumping on the initial layer. 

Usually for cut/pumped 1/4" stars I would only apply 3 primed layers. One application of prime per layer.

Using stars that are geared/tuned towards a higher critical wind velocity. Also helps. Its not all just about the prime.

[pyrokid]

It may be worth testing a toro type process where the prime is made into a slurry then pasted on to the stars. Stars can be rolled by hand with a suitable container.

[Norsepyro]

I would too recommend trying the toro method when priming pumped stars. Make a slurry with the consistency of thin yoghurt which you roll the stars in first so the slurry is evenly distributed. The amount must be measured, and is done by trial a couple of times first. Then sprinkle the prime powder on top until no more is picked up. The stars should be dried when a 1mm thick layer is reached, else they will often pick up prime from each other and become irregular in my experience. My experience is also that sgrs works best for this method. Dextrin gave me a more irregular coating.

I really found the toro method to give a more even coating than simply moistening the dried pumped stars with water spray, following with prime powder.

You can use the spray after the initial toro/dry powder has coated the stars and you then want to add some more prime powder. It is when the stars have a dry surface that the sprayed water just seem to be absorbed into the stars, without giving much effect to letting the prime powder stick onto the stars surface. 

[Carbon796]

Using the two bowl method, like you are currently. Is perfectly fine. You don't need a star roller to apply prime evenly/uniformly. You are essentially hand rolling them, in the second bowl. I preferred to use the two bowl method. To more easily control the quality of the priming process.

Edited April 6 by Carbon796

[gizmothegecko]

When I use the two bowl method it take me 4-6 times to thoroughly step prime them because I let them dry after each layer, so I think I'll try the toro method.

This is the method I originally used by Ned and it worked really well for some stars, but other crumbled:

https://www.youtube.com/watch?v=gSrbj-vn9-g&t=269s

[Carbon796]

If I put 4-6 layers of prime. On a 1/4" star, it would probably be almost 7/16-1/2". 

What is the percentage of weight gain. After you've put 4-6 layers of prime on them ? 2-3 layers should get you in the 25% -30% range.

For a hard to light star in shells. One layer would be 50/50 star comp/hot prime. One layer hot prime. One layer scratch mix. And you're done. For general purposes stuff. Just one layer of hot prime and one layer of scratch mix. Should be enough.

The Toro method is really more suited to, rolling precision round stars. Rather than priming pumped stars.

[gizmothegecko]

They are probably 5/16 at best. I don't use a dissolved binder solution, so that is probably the problem. Could you specify what binder I should be dissolving in my solution? I'm pretty sure Ned went over this in a video I saw, so I will refer to it. The only problem is when I used a dissolved binder solution, my blue stars crumble, but that could be because of an error I made, so I will pump out a small batch a retest. 

Edited April 8 by gizmothegecko

[Carbon796]

The most common is dextrin.  Usually at 10%. You should still have binder in your hot prime/BP scratch mix prime. It is generally boiled to dissolve the solution. 

Keep in mind that it goes bad/spoils. The warmer it's kept, the faster it will spoil.

Personally I've always preferred SGRS. Both for star binding and priming. I feel that it has better advantages than dex. In most cases.

Gum Arabic is also used in solution sometimes, iirc.

 

[gizmothegecko]

Makes sense. When I tried dissolving the dextrin it turned into a big clump. All of my formulas use dextrin from Zopetes' star family. Thanks for all y'alls help.

Edited April 11 by gizmothegecko

[Zumber]

Toro method is suitable for SGRS. Most of japnese composition rely on SGRS as a binder. Dextrin can be used, but in toro method appropriate viscosity of toro is very important. Also temperature of star which is to be coated with next layer is important thing, stars are kept in a shadow for and hour or two before it is coated with next layer or prime, if temperature of star is high (just in case if  just right after it is taken out of sunshine and shifted for coating) then it absorbs moisture faster from toro and becomes wet and may crumble sometimes or face difficulty in working. Solution of gum arabic tends to become acidic after time and not suitable for sensitive stars.

You can make rolled stars in bulk without having a star roller and it can be easier to work with it regarding priming, bulk production etc. 

There are few tutorials /information available to roll stars manually without star roller.

 

Edited April 11 by Zumber