pasting technique

[pyrochris732]

This might be a silly question but how do you guys get your shells so smooth? My little 2"ers are all wrinkly. I use 1 inch gummed kraft tape from pyrodirect, if that makes a difference.

 

I used 9 layers of this stuff and it fits the mortar quite well. I dont think im doing anything wrong, and i cant figure out for the life of me how you can get such straight smooth lines on your shells. Is this kraft tape no good? I just dont want to have sucky shells since im upgrading to 3 and 4 inch shells soon.

 

 

[TheSidewinder]

Part of the problem is that you aren't saturating the tape to the point that it CAN be pressed completely smooth. (Yes, a Wasp machine can accomplish that smooth finish, but it's part of an extra step called 'burnishing'.)

 

Using traditionally pasted Kraft paper, it's fully saturated and can more easily mold to the curvature of the shell as it dries.

 

That's an over-simplified explanation, but... basically the reason.

[Mumbles]

Your shell is wrinkley because the tape is too wide. I can barely get 1" wide tape to lay smooth on 4" shells. I use 3/4" for 3", but I bet it would work okay on a 2" shell. One way to make it lay smooth is once you have a layer on, wet the surface a bit and roll the shell against a hard surface to flatten everything out. I cheat a little bit too. All of my shells are pasted in odd layers. I use however ever many double layers, and then I lay a purposely pretty single layer on the top, making sure to get the tape good and wet to adhere well.

[Arthur]

Narrow tape is a good start -for a 2" about 10mm is a good start. OR use pasted paper soaked for a while in paste so that it lays well in wider strips.

 

Remember that the Chinese use lots of layers then sand the outside round, then paste a final layer decorously.

[AdmiralDonSnider]

One way to make it lay smooth is once you have a layer on, wet the surface a bit and roll the shell against a hard surface to flatten everything out.

 

 

True. Shimizu describes the use of a rolling board to make the pasted kraft adhere well. With gummed tape it may indeed be difficult.

 

Especially for small shells I often use a smooth wooden dowel to smoothen the layers by hand while holding the shell. You don´t need to do this after every layer, but it gives the best finish if done.

[Mumbles]

I think it does more than just making it pretty for gummed tape shells. I do it every layer or two. In addition to making it pretty, it serves the positive function of laying down all loose edges

[jwitt]

I had a similar problem with 3/4" tape (same vendor) on a 3" shell. My shell is lumpy as all get-out! However, I found that the tape behaved better when it wasn't totally saturated- it stuck better, the glue was more tacky and less slippery. It seemed that my method of smoothing the tape once it was laid improved too, pressing away from the center and smoothing the edges that show on the final layer.

 

I've seen the wooden dowel used to burnish a shell in a video- it would be the same dowel you would use to bang the shell hemis together.

 

Also, by my last layer, I had the 3-strip method down. That is, I learned how to make the pattern even, so the last layer is smooth, but shows the lumps and bumps from the layers below.

[Bonny]

I've never made 2" ball shells (and never will), but for 3" I use 1/2" to 3/4 wide strips of 40lb paper.For 5" shells I use 1" - 1-1/4" strps of 50-60 lb paper.

I soak the strips in paste and crumple several times to break the paper. Add more paste if needed.

I never did figure out the 3 strip method, and gave up after a few tries. I use a similar method to the one found here:

http://skylighter.com/skylighter_info_pages/article.asp?Item=112#shell

I overlap the paper by 1/2 and fill in the ends on each layer. My shells come out looking really good (not perfect). I do 2-3 (double) layers at a time. Wait for the shell to dry a bit and roll it on a board or table to smooth if needed.

[pyrochris732]

thanks guys, very helpful. Pasting takes forever! But, it should be a nice payoff when the 4th of July rolls around and I get to hear the ooos and ahhhs!

[jwitt]

Huh. I did lots of pasting last night and once again feel that less-wet tape works nicer. I got much smoother shells by laying down the center of the strip, making sure I'm centered on the poles, securing the ends so they don't have any wrinkles, and then lightly pressing the long sides of the tape down. The wrinkles on the long sides "averaged out" and actually made a consistent pattern around the shell. I then burnished each layer. I found that this method was faster than taking lots of time to smooth each individual strip. Burnishing with sort of a potato-peeling motion from the center of the strip to the pole worked well to stretch the paper a bit. The less-wet tape is really really tacky and made this work well.

 

The only "problem" as it were is that now my 76mm / 3" shell finishes off at 68-69mm instead of 71-72mm with 5 turns of 3-strip since things are much more compact and smooth. I think I'll be able to compensate for this by making my 3-strip strips a bit closer together.

 

They actually look sort of like shells from the guys here who know what they're doing!

 

 

PS I used the slightly curved sides of a metal utility knife to burnish- that might work well even on the 2" shells?

Edited May 18, 2010 by jwitt

[50AE]

You should also have in mind, that you have to push with a quite good amount of force using your fingers, to make your shell's surface smooth. Take a look at my video at 04:34, I do this using my two thumbs, pulling and pushing in the opposite directions.

 

http://www.youtube.com/watch?v=ovrBlo-ic68

 

When you watch it, it may seem that I'm just sliding my fingers. But in reallity, I push very hard and there's excess of glue coming out the paper.

Edited May 18, 2010 by 50AE

[jwitt]

Your video taught me how to do this!

 

Final smoothing of the strips- what you are doing with your thumbs is what I'm doing with the back of the knife handle. Gummed tape doesn't seem as nice to work with as strips and paste though, and I couldn't get the wrinkles out with just my hands.

[50AE]

Yes, gummed tape is rougher to work with. When there isn't enough water on the tape, the glue hardens fast and it's hard to get rid of the wrinkles. But with strips and paste, it's another thing. They are soaked in very much water and glue, and you have time to smooth them. Edited May 18, 2010 by 50AE

[leosedf]

Well...

I never had a problem using gummed tape. Even reinforced one. All my shells come out perfect round and smooth.

http://www.youtube.com/watch?v=MG4830y5FE8 on my vid (still missing part 3) i think you can see how it works.

[50AE]

Your method seems very labourious to me. I've never liked pasting with gummed tape.

But that's everybody's taste.

[FREAKYDUTCHMEN]

My taste neither:

http://www.pyrotube.com/videos/391/pasting-a-6

 

Chris, dry between 2 layers, and the bigger your shells are the less the wrinkling is.

[50AE]

FREAKY, I think I'm going to "steal" your pasting technique.

 

At least I'll try it on 3". It saves great time cutting the paper into small strips.

[Mumbles]

There are definitely faster ways to use gummed tape. I take an arm span full (6 feet or so) and run it through a wet wash cloth. This wets both sides, and really helps it lay down nicely (and prevents paper cuts). From there, I start laying down double layer strips leaving a pole at both ends. I tear it off as I lay it down, something like Freakydutchman does, just not in the 3 strip method. Fill in the poles at the end with paper for a complete layer. The shells come out very round. It took me approximately 25-30 minutes to paste in a 5" ball shell a few weeks ago with 15 total layers.