Prime do not want to stick over pressed stars!

[MinamotoKobayashi]

I have wasted many batches of red and green stars in several tries and I do not understand where is the issue!

I have a star plate and an hydraulic press, and I have successfull pressed Willow Diadem Tiger Tail Extra (do not needs prime)

and Golden Glitters (modified by NeighborJ with MgAl) primed successfully with pulverone plus 5% dextrin plus 5% 325 mesh MgAl).

I have also pressed Barium Nitrate (for the green) and Strontium Nitrate (for the Red) stars, modified by NeighborJ in that way:

 

GREEN

Barium Nitrate

Potassium Perchlorate

MgAl

Parlon

Sulfur

Phenolic resin

 

RED

Strontium Nitrate

Potassium Perchlorate

MgAl

Parlon

Sulfur

Phenolic resin

 

 

Since these stars ignite easily, but needs prime anyway, I tried to prime it with BP meal plus 5% 325 mesh MgAl.

First I putted all the stars inside a kitchen strainer, I carefully wetted them with a spray bottle that contain warm demineralized water plus some

dextrin (a table spoon every litre as NeighborJ suggested me), and then floured the stars into the prime.

Well, about half of the stars refused to stick the prime, and the other half had a weak adherent prime that comes off during the break.

I tried many variants, such as replacing the isoprophyl alcohol with acetone or with denatured alcohol in the star compound,

or replacing the phenolic resin with red gum ... same soup.

So, where is the problem?

I have in mind only two possible issues: the star walls are really too much smooth and compact (due to pressing the stars with a star plate), or the water plus dextrin plus meal is incompatible with the chem of the stars.

Please help me, I wish to not waste again tons of stars !!

Edited April 1, 2018 by MinamotoKobayashi

[Arthur]

I'm no expert with phenolic resin, so here's just a suggestion or two.

 

1/ drop the plate pins 1/8th of their travel first, add some BP then drop the pins the rest of the way and load star comp - product a star with integral BP prime on one end.

2/ make the stars, then use a viscous mix of meal powder with dextrin in water (viscosity of double cream), dip the dipped star in 2FA or 4FA

[mabuse00]

Did you press your stars dry?

 

 

 

Anyway:

Your stars do not contain any water soluble binder. They wont dissolve from water, or at least not completely.

 

To make the prime stick, you need something that "attacks" them. Since they contain phenolic resin, wet them with ethanol or isopropanol.

 

Then the prme should stick.

 

If your prime layer shall be very thick, you can add a little phenolic resin to the prime also.

[MinamotoKobayashi]

Hi Mabuse, thanks a lot for Your hint.

 

Usually I press the compound slightly wetted with denatured alcohol. The most important thing is to found everytime the "sweet spot" in order

to create a compound with the right humidity.

I tried acetone but the stars become too hard. I have also tried isopropanol (isoprophylic alcohol), but it contains too much water

and this water often are trapped inside the pressed stars and do not dry correctly, creating issues with the colours.

 

The stars pressed are perfectly dried inside a drying machine for 24 hours.

 

So You suggest me to wet the walls of the stars with isoprophl alcohol and them flour them with the prime?

But my prime contains fast meal BP (charcoal plus sulfur plus KNO3 plus 5% dextrin) and another 5% of MgAl 325 mesh.

Are You sure that this mix is compatible/soluble with isoprohyl alcohol?

Edited April 1, 2018 by MinamotoKobayashi

[Baldor]

Why not try 50/50 water and ethanol? ethanol should soften the surface of the star, and the water activate the dextrin in the prime. Or use a very thin layer of NC or phenolic binded prime, so you have some rugosity, then your preferred prime.

[Arthur]

I once made dextrin stars with boiling water. They stuck like concrete in about 10 minutes. Hard enough to drill.

[MinamotoKobayashi]

x Mabuse:I tried to wet the stars with isoprophyl alcohol only. Of course the dextrin in the prime was not activated, so the prime slipped away leaving the stars naked.

 

x Arthur: I haven't understand Your procedure .. can explain it better please?

 

x Baldor: I will try 50/50 water and ethanol.

There are sever kinds of ethanol: the one used to make liquors and bio-ethanol for the stoves.

Can I use the second choice? Is much more cheaper!

Edited April 1, 2018 by MinamotoKobayashi

[Baldor]

It´s the same. The second one have additives to make it not drinkable, but for our purposes is the same.

[mabuse00]

The dextrine in the prime isnt necessary at all.

When you habe a star containing an alcohol soluble binder and wet it with alcohol it leaches enough binder into the prime to make it stick.

 

(I have to admit that I have some phenolic here but I've never tried it out )

 

 

You need pure alcohol! Not some 50/50. Isopropanol should be 99% or so. That is available OTC here in Europe.

95% denatured ethanol should be fine also.

[Mumbles]

A 50/50 mix will probably activate neither the dextrin or the phenolic resin to any appreciable degree. Dextrin is activated solely by water. The degree of this activation decreases with increasing quantities of alcohol. The inverse is true of phenolic resin. I'm not saying it wont work, just that it probably wont work optimally. All you probably need to do is tack up the surface a bit to get the prime to start sticking, and then it will likely take care of itself.

 

The issue is probably the slickness of pressed stars combined with the non-aqueous binder. When stars are a bit more rough, even when bound with non-aqueous binders they should never have an issue with adhesion, even if there is not a common solvent used. You may want to try adding a perchlorate, resin, metal based hot prime. Something like monocapa, or the veline super prime (with some modifications), or pinball prime would be prototypical of the type of prime I'm talking about. Even when bound with alcohol, these have no issues with adding water bound BP primes over the top. They also burn nice and hot and help to ensure ignition.

 

A light dusting of prime is rarely enough, which might be your issue to begin with. A layer of at least 0.5mm to 1mm is recommended, if not thicker.

 

You may also want to research the Toro method of star rolling. It uses a slurry of composition to wet the stars instead of straight solvent, and then dry composition to dry it up. This works great for applying primes too. I suspect part of the issue might additionally be that you're trying to baby the prime onto the stars.

[MinamotoKobayashi]

Hi Mumbles.

I have just found this interesting old topic in another forum:

 

http://www.pyrosociety.org.uk/forum/topic/6392-pinball-prime/

 

.. and there is also a reply from You

 

Yes, the mix 50/50 doesn't work because the alcohol create issues with dextrine.

In fact when I wet with a spray bottle the stars before to apply the prime in the water-based stars, I use only warm demineralized water plus a table spoon of

dextrin every litre plus 2% only isoprophyl alcohol to reduce the surface tension (thanks to NeighborJ for the hint )

 

Right, the main concern is the smooth walls of the stars created by the star plate.

Carbon based stars like Willow Tiger Diadem and golden glitters stars use water and dextrin in the mix ... with these kind

of stars I never had any sticking/ignition issue using the star plate and a normal prime (usually pulverone plus 5% dextrin plus 5% 325 mesh MgAl).

 

NeighborJ use the "cutted star" technique that make the stars surface very rough, and with this technique the prime cling well without any issue.

Unlucky I had a 2 KG batch of 1cm diameter red and green stars created with star plate, and before to make cutted stars I wish to use these stars.

They are easy lo light, but they needs a prime anyway. Sincerely I'm in difficult to decide how to solve the sticking issue but I read many positive

reviews about Monocapa and I wish to try it.

The Veline superprime uses Potassium Dichromate that I'm unable to find everywere, that among the other things is toxic and carcinogenic ...

 

I know the Toro method but usually I have seen it to making stars, not to make coating ...

Edited April 3, 2018 by MinamotoKobayashi

[MrB]

I tried acetone but the stars become too hard.

Wait... Define "to hard"?

Honestly, i can see not wanting to use acetone due to cost, but if the star is an indestructible object after drying, i'll be fine with that. Also, if you do bind it with acetone, a slight misting would make it tacky enough to stick on the next layer of composition, be it prime or anything else, and if this i a dextrin bound composition, then letting the acetone evaporate, and hit it with some water should let you add more of the later composition...

 

I know the Toro method but usually I have seen it to making stars, not to make coating ...

It works just fine for coating, turning cut, and pressed stars in to round ones.It wont be an "even" coat, since flat sides will try to turn round, but it lets you build up a good layer. Can be a bit of a chore to get the stars tumbling nicely if you have a smooth barrel.

[MinamotoKobayashi]

I stopped to use acetone with my star plate for three reasons:

 

1. The toxicity of the acetone itself. I work in a small room and my two-filters professional dust mask are not suitable to filter the exhalations;

2. The difficult to maintain cleaned the star plate. Often the two parts stick one to another and I had many difficult to separe the parts;

3. The stars become even more hard and the star walls even more compact and smooth, getting even worse the prime sticking problem.

Surely, with this kind of stars, I will be forced to handly create rough cutted stars, as NeighborJ suggested me long time ago ...

Unluckly, for my rounded shells, it is a pain to arrange square stars around a curved surface.

Edited April 3, 2018 by MinamotoKobayashi

[Juanma9410]

Hi, I use phenolic resin

What percentage of each chemical carry your green and red stars?

[NeighborJ]

I am not quite comfortable posting the two green and red formulas yet. They worked great for me as easy lighting cut stars, they seemed to pose other issues when pressed. On top of that, i found it necessary to use different mesh size MgAl to get the timing close. The green accomplishes its goal of easy ignition but at the cost of being a slightly dirty color.

 

I plan to pick up this project again to resolve these issues but i dont know when. There are plenty of awesome color formulas out there such as the ones on the jopetes PDF file. They light fairly easy with monocapa and I've not had issues using phenolic resin with them.

 

In the end, i really don't see the need for more formulas to be created unless it exhibits some new great redeeming attribute, there are already too many average or outdated formulas which can make choosing one a chore.