Kraft paper for pasting small ball shells?

[PyroFrank]

Hey everyone, I'm planning on making some small ball shells this summer (2" - 3"), and I'm thinking about changing my pasting method from gummed tape to virgin kraft and wheatpaste. I was wondering if anyone knows what would be the best paper weight to use, and where you like to buy from? I was thinking about buying this 50 lb roll here.

 

https://www.qualitypaperforless.com/prestashop/en/specialty-paper/25-virgin-kraft-50-lb.html

[lloyd]

For small shells, 30lb to 40lb is about right. I'd use 30lb for the 2" shells, but understand that it requires more layers than the heavier paper. 50lb will work, but you'll spend more time smoothing layers, and will - of need - have to use narrower strips to get it to lay reasonably flat on the spherical surface.

 

Make sure it's "virgin kraft", and properly "break" the paper with paste before applying it -- you can't just 'paint on paste', and stick-down the paper!

 

Lloyd

Edited April 23, 2017 by lloyd

[OldMarine]

I'm trying to learn to paste with discs rather than strips and am getting better at it. The 40# works well for me as far as being able to smooth it down but I can't speak for the breaks and containment since I've only been building dummy shells so far.

I got my paper from Uline:

https://www.uline.com/BL_1142/Virgin-Kraft-Paper?keywords=Virgin%20Kraft%20Paper

[Mumbles]

I don't think you'll see much difference between 30 and 40lb. Both should work fine and lay down well. On smaller shells like 2 and 3", sticking to thinner paper makes sense. Bigger shells can take thicker paper, which also can save on layers. Let us know what you think of the kraft and paste pasting. What sort of pasting method or pattern do you plan on using?

 

You probably wont have to deal with it on 2 and 3" shells, but you don't want to paste more than 6 or 7 paper layers at once. This can cause shells to get sort of spongey. In many pasting methods this comes to 3 double layer applications.

[OldMarine]

Mumbles, how many more layers of 30# paper would be required on a 3" as opposed to using 40#? I have a couple of 36" wide rolls of the 30# and wouldn't mind using it for smaller shells if it isn't a ton more layers.

[lloyd]

Now, Patrick, we get back to that "math issue" you once described.

 

For sake of comparisons, it's useful to think of 'pounds' as 'thousandths of an inch', when describing papers (and it's not just a ruse, for examples; in fact, pound-basis also comes very close to being matched by thickness in 'thou'.)

 

So... one layer of 30lb would be 0.003"; one layer of 40lb about 0.004".

 

Three layers of 40lb would make a thickness of 0.012". Four layers of 30lb would make the same 0.012" thickness.

 

In fact, the paste adds a tiny bit of thickness per layer, also, but it can very-nearly be ignored for figuring how many layers to put on.

 

Lloyd

Edited April 23, 2017 by lloyd

[Mumbles]

As an example, I usually apply 7 layers of pasting to a 3" shell. Going by thickness this would be .021" thick. If switching to 40lb paper, the closest equivalent thicknesses would be 5 (.020") or 6 (.024"). This assumes that thickness is the only thing that matters, and similarly that the 40lb paper is 33% stronger than the 30lb paper. I honestly can't tell you how true either of those assumptions are, and will likely vary between manufacturers. It's going to require at least a little dialing in. This is going to be true when switching from gummed tape to pasted paper anyway. My gut says that 6 layers of 40lb is more suitable than 5, but that's not really based on anything particular.

 

If you want to read more about this, I'd suggest section 16.4 in Fireworks, Art, Science, and Technique by Shimizu on pasting warimono shells. He developed a relationship between the number of layers required, the size of the shell, and tensile strength of the paper. Kyle on passfire.com did some testing of his own, and put up some numbers for paper that was available at the time. The relationship is given below.

 

N = (5.6 * D)/J

 

N = number of layers

D = actual outer diameter of the shell (in cm)

J = mean value of tensile strength, measured both parallel and perpendicular to the grain. (in kg per 1cm width)

 

This is more to illustrate that the number of layers is tied to strength and not always directly to thickness. I've never actually used the relationship, but thought it might add a little more to the conversation and provide some background.

[lloyd]

"This assumes that thickness is the only thing that matters, and similarly that the 40lb paper is 33% stronger than the 30lb paper. I honestly can't tell you how true either of those assumptions are, and will likely vary between manufacturers."

-----------------

I agree -- It is, in fact, an 'assumption', Mumb. But among 'true' virgin kraft papers, the strengths very-much correlate with thickness, and there's not enough difference between vendors' papers to matter much (because they all use the same process, and in fact, there aren't a LOT of mills, even though there may be many brands, at retail.)

 

Papers like "Kozo" don't compare well to kraft. Use Dr. Shimizu's recommendations for those papers, too!

 

Lloyd

Edited April 23, 2017 by lloyd

[OldMarine]

I hate when you all give reading references because I can't stop reading at the end of the prescribed section. Now I want to build a poka shell.

[PyroFrank]

This is very helpful, thanks for all the info guys! I'll probably go with the 30 lb since it's the best deal and I'm most likely sticking with 2 and 3" shells for the time being.

 

Lloyd, you mention having to break the paper before use, is this very critical? My plan right now was to build a glue box, much like a user on here named Col did. I want to cut long continuous strips of paper and wrap the shells like a pasting machine would, and just switch the poles every layer to prevent build up. The only problem is now I'm thinking the paste might not get adequately worked into the paper.

Edited April 23, 2017 by PyroFrank

[OldMarine]

I've found (the hard way) that breaking the paper not only gets the paste into the paper but allows it to lay better on the shell. This makes smoothing and getting air/paste pockets smoothed out a cinch. Skip that step and you'll need a burnishing tool much stouter than your thumbs and you'll still have an ugly paste job.

[lloyd]

Frank, I, personally, would not apply kraft paper with paste (dextrin glue on 'tape' isn't the same), without breaking the paste into the paper. It's an integral part of the strength of the assembly.

 

Lloyd

[OldMarine]

Ned on FW has an excellent video on the disc method but this very talkative Russian guy will give you the gist of the process. I hopefully started this at the point he actually starts doing something...

https://youtu.be/EjDkyrSEWUc?t=27

 

My bad, he's still just yacking.

Edited April 23, 2017 by OldMarine

[hanabi24]

If anyone needs 40# virgin kraft, I am selling 100' x 24" rolls for $32 shipped.

 

btw I am the same Hanabi from fireworking.com

[OldMarine]

Virgin?

Edited April 27, 2017 by OldMarine

[Sparx88]

50 lb is perfect, I use 60lb and it's at the edge of too thick for some things like small tubes but for pasting shells it's great. With the 50lb let it get completely soaked (when it gets dark brown) with the wheatpaste so it will lay down and stay down on curves. 3" ball shells get 4 layers same as 2" with 60lb so add another layer for 50lb paper. Also I use a blend of tight bond original 30% and 70% wheat paste. Much stronger bond and hardness than just wheat paste alone and even casein glue.

[OldMarine]

I use rinfasciature on my cylinders and I'm only beginning in ball shells but am trying the disc pasting method. I've been using 40# but the 30# lays much smoother. 50# would probably be like sewing a baseball in pain factor.

[Sparx88]

Once it's completely soaked it lays just as good because I have 30lb too. 4 layers of 60lb is eq to 8 layers of 30. So unless you really really like pasting, less work and materials for equal and sometimes better results is king For anything smaller than a 1 3/4 ball it's 30lb for sure.

Edited April 27, 2017 by Sparx88

[Sparx88]

Sorry that last post of mine reads a bit like a wise ass. But I -was- trying to help though. With the paste made like I make it, has very high tack after a few minutes out in free air. I wrap the wet strips in plastic wrap until soaked and then "-broken in-". Negates most of the laying down issue.