HomeForum

Forum

Note: The forum uses a separate login system to the galleries.

You are not logged in.

Options

Strength question for large balloon

#1 2015-10-18 04:47:24

jdiver
Member
Registered: 2015-10-18
Posts: 3

Strength question for large balloon

I'm creating a Halloween costume in part by applying paper mache to a 36" round balloon. My plan is to apply 4 coats of paper mache (I'm at 2 coats now) and then a coat of gesso. My concern is that due to its size it will collapse, and unfortunately I won't really know how strong it is until I remove the balloon. Has anyone done something of similar scale who could offer some info or advice? Would more coats of paper mache be better? I'd hate to spend all the time on it only to have it collapse on me. Thanks in advance.

Offline

 

#2 2015-10-18 07:20:16

CatPerson
Moderator
From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1301

Re: Strength question for large balloon

The first test would be when it is dry, push in on it with your finger.  That can give you an estimate of how rigid your two layers are. 

What kind of paper are you using, newspaper, copier paper? And what kind of adhesive are you using?  I hope it's not flour for something that size.

Personally, if you've been using newspaper, I would add a couple layers of "harder" paper, like copier paper (used is fine), and then push against it again.  To use larger pieces of paper (that sphere has about 28 square feet of surface), try using triangles instead of strips, the largest that will work.  TEST the size before you cut out a lot of them!  And make sure you overlap them.

I've never made anything that large that has no central support, so I can't say how many layers you'll need. But I suspect that it will still be "delicate" and will dent if you hit it, or bang it into something hard, or drop it.

I just can't think of anything else that would provide strength. Coat it with polyurethane?

Good luck!

Sue

Offline

 

#3 2015-10-19 00:46:59

jdiver
Member
Registered: 2015-10-18
Posts: 3

Re: Strength question for large balloon

Thanks for the reply. I've used newspaper for the first 3 layers and am using a recipe of water and flour (uh oh) that I found on this site. (http://www.papiermache.co.uk/tutorials/ … ier-mache/) I think what I'll try is 2 layers of triangles with watered down PVA glue and triangles of copy paper as suggested.

Have you ever coated paper mache with gesso? Several blogs I've read elsewhere have recommended it, but my concern is that whatever strength it might add will be offset by the weight it adds to the structure.

I guess I'll just cross my fingers and be very, very careful. lol

Offline

 

#4 2015-10-19 01:10:10

CatPerson
Moderator
From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1301

Re: Strength question for large balloon

I don't think gesso is all that heavy when it's dry.  Modern gesso is usually a mix of something like acrylic paint mixed with chalk (calcium carbonate).

Most of my experience with large hollow spheres is using concrete, and I've had to let one side harden before it was safe to turn over and do the other side.  And with concrete, I've included fibers; but my only experience with fibers and papier mache has been winding string around it, and for something that size, you would probably need a mile of string!

You've probably already discovered that setting your sphere in a container holds it steadier than chasing it as it rolls around a flat surface.  For something that size, one of those 22-gallon plastic tubs would probably be ideal.

Good luck!

Sue

Offline

 

#5 2015-10-19 10:10:22

dopapier
Moderator
From: UK
Registered: 2004-12-04
Posts: 746

Re: Strength question for large balloon

It is all very experimental, but what fun!  The idea of reinforcement takes me down a slightly different path.  If you were to make it in two halves or with a cutting line to separate the hemispheres you could reinforce it from the inside before putting it together again.  It would mean making the two edges of the cutting line as strong as possible (even with wire embedded in the paper).  For the inside, think of the ribs of a boat.  You could bend cardboard to that sort of shape and glue it on the inside.  Pierce holes along each of the two edges and stitch them together before covering with more paper.


I'm a PM addict

Offline

 

#6 2015-10-20 19:06:12

jdiver
Member
Registered: 2015-10-18
Posts: 3

Re: Strength question for large balloon

I put a 4th layer on using a PVA glue mixture with triangles of copy paper. It definitely seems more solid. I plan to add a 5th layer tonight or tomorrow, and then see where it's at and (hopefully) remove the balloon.

I've read a number of places to not add more than 4 layers. Is there a reason other than it makes it thicker and maybe more difficult to cut?

Cutting the sphere in half and reinforcing it from the inside, then stitching it back together, is a fantastic idea! Worse case scenario, if I remove it from the balloon and it crushes, then all is not lost!

Thanks for the ideas!

Offline

 

#7 2015-10-20 20:07:50

dopapier
Moderator
From: UK
Registered: 2004-12-04
Posts: 746

Re: Strength question for large balloon

There is literally no limit to the number of layers.  It is just a question of drying.  Someone obviously thought that you couldn't do more than four layers at a time without retaining some moisture.  It all depends upon your drying conditions, general humidity etc.  I've achieved an incredibly strong sphere (much smaller than the one you are doing) by making a strong layer structure and then topping that with pulp.  However that is a totally different ball game (ha ha)and you really need to know what you're doing.


I'm a PM addict

Offline

 

#8 2015-10-21 07:10:10

CatPerson
Moderator
From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1301

Re: Strength question for large balloon

"I've read a number of places to not add more than 4 layers. Is there a reason other than it makes it thicker and maybe more difficult to cut?"

I've read things like that, and I believe it's more of a drying issue. Especially when a plastic-type glue is used (like PVA white glue), if the thickness is too great -- built up all at once, the adhesive wants to dry on the outside and stay moist on the inside, which would be counterproductive for drying and strength.

In my personal opinion, you could add many layers, as long as you limited each set to maybe two or three layers, and then made a point of letting them dry thoroughly before adding more.

By the way, did you leave the "mouth" of the balloon or ball exposed so you could just open that to let the air out?  It's handy to do it that way if you use those exercise balls and inflatable toys, and then you can use them again.  Although, by the time you're finished with this project, you may be tired of doing large spheres, and be perfectly happy to stab it to let the air out. ;-)

Sue

Offline

 

#9 2015-10-21 20:52:18

Jackie
Moderator
From: England
Registered: 2002-09-14
Posts: 387
Website

Re: Strength question for large balloon

Makes a wonderful sound once you've stuck the pin in....as the rubber balloon rips itself from the inside edges! (Little things, I know!)

I always use 7 or 8 layers. Just need to make sure you work in a room with an even temperature when working with balloons, and don't get the dried areas too wet with the additional layers. If it does all go wrong for you though, you can usually turn it into something else. Just tell everyone that  you planned it like that all along! 💡


Jackie

Offline

 

#10 2015-10-22 20:40:39

CatPerson
Moderator
From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1301

Re: Strength question for large balloon

Oh, Jackie!  You're giving away my secrets!

Sue

Offline

 

Board footer

Powered by PunBB
© Copyright 2002–2005 Rickard Andersson