moisture % for pressing stars

[pyronoob]

I'm wanting to start pressing stars with my new star plates....how much moisture/liquid do i need to use...When i cut i'm using about 18-20%...plus im subbing phenolic resin for the dex in my comps.

 

Thanks

[Carbon796]

If your using phenolic for binding to pump with. A general recommendation is 6% denatured alcohol. Then you can fine tune your own personal preference per comp, from there. I personally, usually use less than 6 % but its a good starting point. Edited January 24, 2017 by Carbon796

[lloyd]

Russ, I'm glad Carbon jumped in. I have pressed (actually) millions of comets, but never once used phenolic in a production setting -- so I'd have to refer that to someone else.

 

With dextrin/water in Black Powder type compositions, I tend to use about 5%-6% dex, and 3%-6% water. Like Carbon, I find that less water is usually better.

 

However, when using scant amounts (like 3-4%), it takes quite a while to fully activate the dextrin, so I've been known to mix at 9-10pm, then let the batch sit overnight before pressing.

 

I like to press comets at about 1500psi on the composition.

 

Lloyd

[Arthur]

It's really up to you! Somewhere between 2 and 6% solvent would be likely. Too much and the comp will flow under pressure and may make a mess! With amounts under 10% it's hard to apply and mix it evenly, so a period of hours in a sealed plastic bag usually helps. Too little and the binding will be patchy.

[pyronoob]

Thanks folks. Lloyd i have heard that it does take some time to activate. Thanks for confirming what i heard.

[calebkessinger]

I've been having good luck at 5 to 6 % then screening the comp 3 times through a 12 mesh screen to distribute the water evenly then immediately go to pressing them.

Here is a vid of me doing just that.

I could probably lower the moisture a freckle to keep the plate a bit cleaner but overall it works well.

Wait a sec..

I just noticed your name.. Why don't ya just come by some evening and press some stuff up?

[lloyd]

Caleb,

I've pressed dextrin-bound BP comps in as little as 1/2-hour after wetting. It works, and we got the batches out. But it's MUCH dirtier than if allowed to sit (especially with less moisture) for a longer time.

 

We were doing up to 9K crossettes a week from BP comps in our shop. We did everything we could to minimize cleaning of the mold and pins during the sessions, due to the time lost doing it.

 

Lloyd

Edited January 24, 2017 by lloyd

[calebkessinger]

I think I'm gonna have to try it with less moisture then.

 

I kinda figured there was a cleaner way and the factory doesn't have to fool with cleaning the mold every few pressings. Although I did notice pressing those upside down like that with delrin pins it only took a quick brush off with a paintbrush and all was well. I'm thinking from here on out I'm gonna try to make things press upside down like that. It sure saves a lot of time fooling around.

[lloyd]

FWIW, Delrin tips on the flat pins makes a huge difference, too. You can go for a half-hour sometimes without doing anything more than just brushing it off.

 

Lloyd

[calebkessinger]

I haven't tried spraying them with mold release yet and seeing if it makes a difference. That is what I spray on my nosecone formers to keep the gummed tape from sticking.

[pyronoob]

Caleb, i'll probably take you up on that....you have a nicer press...

[Seymour]

I'm going to agree that when pressing cylindrical stars or comets, less solvent is often better, but as Lloyd said, not so low as 2-3% usually.

It depends so much on the composition! Many colours will only need 4% with dextrin. High carbonate ones might be better with 5%. High charcoal compositions tend to need more water no matter what method you use (rolling, cutting, pumping), but with pressing my experience is that the difference is less. I'd say 5%, maybe 6% depending on the composition.

It also depends on how hard you press them! The harder you press, the less solvent is required as a general rule.

For Phenolic resin (Resinox/Lac resin) I've personally found that 5% is good, 4% ok, but 6% is too much, buy again, this depends on many factors. I've been pressing quite hard. I find 6% results in not only solvent, but a slurry of composition leaking out the gaps in the tooling.

But as I said before, it depends on the composition and how hard you press it.

[starxplor]

I have pressed basic charcoal streamers using 8% water with good results

[pyronoob]

i've done my first batch of pressed stars 3/4". used 5% with phenolic resin....they came out very nice and was rock hard in about 4 hours. Used the blue spanish #1 formula....

[Arthur]

With stars,it's not the hardness (of the surface) but the dryness that matters.

 

Weigh some stars then weigh them later, when they are dry they can lose no more weight.

[OldMarine]

I love phenolic bound stars. A couple of hours in the heat and they're good to go!