Has anyone ever tried this (mated comets, sort of)?

[braddsn]

I want to make some mated comets for shells, for example.. a red star with a long white streamer tail. I have seen pictures of how this is done... gummed tape around the seam of two mated pumped comets. However, I had another idea. What if you were to use a cut star frame, "filled" it half way with one comp, and the rest of the way with the other... in other words, you have a bi-layer square of comp. Then cut the stars... so that in the end, you have a square cut star that is half and half. Hopefully this makes sense. Would this work?

[lloyd]

If they shrank at exactly the same rate and by the same amount when they dried, it might. That's why - most often - it's completely-dried stars that are mated after drying.

 

Lloyd

[limak]

I was attracted by bangkok holidays too It seems to be worth a try.

Never made them before so I'll be experimenting.

Edited May 10, 2017 by limak

[OldMarine]

I'll bet it would work if both were bound with phenolic resin. That rules out glitter type comps for the most part though since I've heard they don't perform well bound with resin.

[lloyd]

Patrick,

You can't predict the shrinkage rate or drying time such that two dissimilar comps will dry and shrink at exactly the same rate, and end up exactly the same size after having done-so -- even if they're bound by EXACTLY the same binding package! Various comps will release solvents at different rates; even the SAME solvent with the same binder! If they vary between the two in the slightest, the joint will fail.

 

It's just not that hard to glue two fully-dried comets together (with, say, NC lacquer/BP mix) and paste them up. And NO, don't do it with 'gummed packing tape'; For heaven's sake, use paste-broken paper!

 

Lloyd

Edited May 11, 2017 by lloyd

[OldMarine]

Yeah Lloyd, I've only done the pasted ones myself and don't find it t be a hassle but it would be fun to find a way to do it with "one-step" cut stars. Hell I actually sat down one night and mated half sized Hardt blue and tremalon stars. Took me an hour to make enough for 2 consumer mines but it was pretty!

[braddsn]

Ok thanks guys, that gives me some food for thought. Different drying rates never crossed my mind, but it makes sense that if there was any variation, the seam wouldn't hold. Might just be better to mate up pre-dried pumped comets. Lloyd you mentioned paste-broken paper. What did you mean by that? The only paper I have experience with (so far) is just the gummed tape that I paste ball shells with. The way I was going to attack it is to hot glue the pumped comets together on one end, then wrap a few layers of gummed tape around the seam. Then prime the exposed ends.

[lloyd]

Brad,

Paper and paste are the tools of shell makers. It's only been since Jim Widmann's introduction of the W.A.S.P. that anyone seriously considered pasting-in a shell with gummed tape.

 

The process is simple, and very inexpensive. It also conforms to irregular surfaces better than gummed tape ever could, and shrinks a lot as it dries for a very tight finish.

 

One takes strips of VIRGIN kraft paper (say 30lb to 50lb in this case), coats them well with wheat paste, and then 'works in the paste' by wrinkling and squeezing and kneading the paste into the fibers of the paper.

 

The paper becomes two or three shades darker, and when uniformly 'broken in', will be as limp and conformable to surfaces as a piece of wet chamois. Any significant excess paste is wiped off before it's applied to a surface, then smoothed. Any 'bubbles' of paste or air trapped underneath are worked out from under the paper, then it's allowed to dry. Sometimes, up to four layers might be applied before drying. Much more than that can trap moisture in the paper.

 

Pasting with 'broken' paper is used (or can be) for myriad pyro assembly tasks. Up until the W.A.S.P. (and with the exception of rinfaciature) this is how most shells of both canister and spherical types were fireproofed and strengthened after assembly, and it's still about the most-useful single skill you could have in a pyro workshop.

 

 

Lloyd

Edited May 11, 2017 by lloyd

[Richtee]

On the old forum I had made a post about using poly “Gorilla Glue” and perc for a trailer... can’t seem to find that, but it sticks well and is bright white unmodified. I think the mix was like 60perc/40glue? Hard to get off yer hands tho

[Maserface]

Married comets are my FAVORITE! But be warned, they take a lot of time. I made some for a 12" shell I'm working on, and I think so far just in the comets I'm over 20 hours to mix, pump (one at a time), marry, paste, and prime.

 

There is at least one guy I know who pumps two color comets in one pressing, his recommendation is lower pressure, higher moisture, and higher dwell time (all relative to "normal").

 

Brad I think you should try cuttin them

[mabuse00]

This is still on my todo list.

 

My solution would be to use cavity star pump, have you thought about that?

The effect should be about what you describe and likely less work-intensive.

 

 

[lloyd]

Mabuse,

 

Even 'cavity comets' have their limitations in terms of shrinkage of the two compositions. Often, with that method, the cavity comet is pressed and dried, and the 'filler color' is poured-into the cavity with a volatile solvent in the form of a slurry -- and in several 'lifts' so shrinkage is not so much of an issue.

 

Certainly, the method works, as evidenced by many folks who do it; but it - also - requires "special effort" not necessary when simply marrying already-dried solid comets.

 

Lloyd

[MrB]

Just to stick out like a sore thumb... I like using gummed paper tape for some specific uses. Of the top of my head, around time-fuses and such. It's much faster setting then pasted paper, so i can get on with it, so to speak.

[lloyd]

It's also much-more-poorly SEALING to irregular surfaces than pasted paper. Quicker isn't always better. When you get your first catastrophic pass-fire from that gummed tape not sealing QUITE enough, you might re-think that strategy, MrB.

 

I happen to like gummed tape for SOME things, but NOT for sealing tightly where fire might pass by for lack of a proper seal.

 

Lloyd

[MrB]

I am of the opinion that it could be leaking like a sieve, and it wouldn't mater, since it's just sticking it there in the assembly-stage, and everything gets pasted once i get to pasting. But if i ever get a flowerpot that i want to blame on the gummed tape, i might regret that call.

And yes. pasted paper is a much better sealer, and has a lot better structural support once dried.

[braddsn]

Ok Lloyd now I follow ya. I have watched many a video of the Chinese shell makers using this method, wheat paste and paper. I only have experience with gummed tape, i guess its time to venture out a bit! I married some 3/4 inch comets last night, and test fired. I tried a few methods with supplies i have in the shop, and every time they blew apart out of the star gun. I tried hot gluing the ends together, then hot gluing a strip of kraft paper around the comets to seal them up. No dice. Gonna have to try the paper and wheat paste trick now.

[braddsn]

Oh and fwiw.. I am gonna try cutting a bi layer patty like i originally described.. I will keep you all posted on how it goes.

[FlaMtnBkr]

I've never thought of hot glue as being all that strong in many applications. If it's going into a slightly dusty star I can see it popping right off. Unless you are using a commercial glue that is a lot softer. Some of them are much stronger and have much better adhesion than the craft store glue sticks.

 

I'm no glue expert but I imagine there are much better glue for the job. Maybe a hide glue? Or like Lloyd said, paste and broke in virgin craft has been used for a century or so for a reason.

[Maserface]

I use brown wood glue, titebond original to be exact.

[Carbon796]

A PVA type glue, like what Maserface used, is what would normally be used to glue the comets together. The problem with the cut star method if they stayed together. Will be the lack of constant timing, for a true married comet effect. Not that it couldn't be achieved with some comps, but your choices would be very limited. Edited May 14, 2017 by Carbon796

[Mumbles]

I would think you'd still need to inhibit the sides even if they stay together. That's the time consuming part compared to the pumping.

 

The biggest issue with pressing or cutting or otherwise forming the comets all in one operation is that the most interesting combinations tend to be the most dramatically different in composition. This makes the variable drying rates and shrinkage the hardest to control and account for.

[braddsn]

Update: So I successfully made a bi-layer patty, and cut 3/4" stars out of it. The 2 comps I used were white pearl, and red (both spanish comps, Jopetes PDF). I used phenolic resin in place of the red gum in both comps, and binded with alcohol. The stars dried quickly. I then primed them with monocapa followed by bp+silicon+DE (this is how I prime most everything). I have fired 4 out of the star gun so far, and have had the exact same results all 4 times. The star fires out of the gun, but the 2 colors immediately "separate" in the air at about 25 ft, and go separate directions. I can only assume it has something to do with burn rate, or that the 2 patties didn't bond well at the seam. I am still gonna put the stars in a couple 5" shells for the heck of it, might look cool. But as for this experiment, I am going to call it a fail. Also another thing to note... making the bi-layer patty was a pain to be honest. Getting everything even was more of a challenge than I had anticipated. Now I know why this method isn't used.

[lloyd]

Heh! Welcome to what practitioners determined up to a couple-centuries ago! <grin>

 

FWIW, it never hurts to 'confirm' old practices once in a while, so long as the work is done with an open mind, and for the purpose of seeing if methods may be improved as materials have improved.

 

LLoyd

[braddsn]

Ha! Yep..... was a tremendous waste of time, I am a grown man but in some ways I feel like a kid.... "gotta learn the hard way and find out for myself".

[Richtee]

OK..here’s what I had found:

 

http://www.amateurpyro.com/forums/topic/3029-a-tip/?p=42336

 

the stuff sticks well..I’d think it would bind to whatever. Colors can be added, but as a brilliant non-metallic white..it’s cool!