This is ambitious.  Flour is not a good paste for this - it is brittle (as you have noticed) and hydroscopic.  Pure PVA will probably be better.
Look through the Forum threads and you will find discussion on boat making and on waterproofing.
DavidO

Thank you for your advice.

Can flour be made less brittle by washing out the starch before and leaving behind the gluten which would be more flexible? Would this need to be cooked to make it stronger? Is anyone familiar with "gluten mache"?

Could flour be made less hydroscopic by mixing in pva wood glue? I think the flour will be a disaster if water gets in.

I am planning to first use the board to surf the tidal bore on my local river which is fresh so salt water wont be a problem initially.

I have done some 2 foot square test laminations on a piece of polystyrene foam and tested their strength by hitting them with a hammer. All 20 layers of paper.

Newspaper and flour - strong but brittle - shatters when hit hard but can resist some gradual pressure.
Brown paper and pva glue - when hit very hard hammer bounces without any damage but prolonged pressure leaves a bit of a dent.
Alternate layers of brown paper and newsprint - not as brittle and seems more resistant.

Ideally I would like to use single sheets of paper for laminating but they seems to wrinkle when wet so torn squares will probably be better.

Shellac - I thought this was a favourite with old fashioned boat builders? Also apparently there is a resin made from soya beans but I would imagine its expensive.

I have used woodworkers glues to increase the water resisitance of paper mache. It still needs a good sealant coat, but Weldbond glue is one of the best, and is non toxic. I understand that it can be used to seal masonry products, but I do know that it makes a great paper mache glue. It dilutes well and is pretty darn water resistant.
http://www.amazon.com/Frank-Ross-Gallon … d_sbs_sg_3

Another, but probably less green alternative, is old fashioned powdered resin glue. This stuff is bomb proof. Has a long dry time and is very water resistant. Almost to the point of being water proof. Again, not the greenest product out there, as it contains formaldehyde, but it will give a very water resistant bond and, when diluted properly gives a nice long drying time for positioning and smoothing paper.
http://www.amazon.com/00203-Weldwood-Pl … OOXWWGTKYX

Last edited by paper soup (2010-05-01 14:57:46)

Laminating your paper together first might help.

One of the things that I do is laminate my paper together in layers before tearing or placing it on my form.  This way the paper doesn't wrinkle as much and saves me time in building up layers and covering large forms.

Basically my set up is a large serving tray (26 x 18) with a sheet of freezer paper taped in the bottom to make clean up easier - (tho I only change this paper out when needed, maybe every 2-3 weeks), some wall paper squeegie / smoothing tools and a squeeze bottle which holds my glue mix (75% CMC, 25% pva).

I then squeeze out a ribbon of glue onto the tray, spread it out, the lay in a sheet of whole newspaper, squeeze another ribbon of glue, spread glue / lay another sheet of newspaper, the cmc/glue mix lets you shift your sheet a bit or lift it up and put it down again to get a good placement ... then smooth it a bit get out large wrinkles), add ribbon of glue, spread it, lay another sheet of newspaper, squeeze glue, spread / smooth.  Then seriously smooth it out - no wrinkles, squeeze layers down. 

Your end result should be 3 layers of newspaper laminated together (making it a bit like thin leather) and ready to either use whole on a large form, or tear into strips for smaller pieces. 

When tearing it, I use something to put pressure on the paper like another newspaper spreader, or a ruler, or aluminum flashing ... which helps the paper to tear in a relatively straight line. 

I got the multiple strips at a time idea from Monique Roberts book http://www.moniquerobertstudios.com/js/book.htm .

I alternate newspaper layers with something else ... copy paper/brown paper ... going in the opposite direction for strength. 

I think the idea of adding a fabric in for strength is a good one ... muslin, cotton sheet.  Those would add strength.

Also, CMC (Methyl Cellulose) can be found at papermaking / bookbinding suppliers or ceramic/pottery suppliers.  The best prices I've seen are at the pottery suppliers (~ $5-8/lb)  Or you can experiment first with a 2oz box of Elmer's art paste - which is the same stuff. 

As for waterproofing ... something like Paverpol might work for environmental friendliness (it's non-toxic anyway) ... but it's expensive.

I would think twice before using Paverpol....see my waterproofing experiment: http://www.papiermache.co.uk/articles/w … ier-mache/

Namely, poor Mad Major who didn't last very long in action.

I am not sure i agree with this:

Could flour be made less hydroscopic by mixing in pva wood glue? I think the flour will be a disaster if water gets in.

I am planning to first use the board to surf the tidal bore on my local river which is fresh so salt water wont be a problem initially.

I have done some 2 foot square test laminations on a piece of polystyrene foam and tested their strength by hitting them with a hammer. All 20 layers of paper.

Newspaper and flour - strong but brittle - shatters when hit hard but can resist some gradual pressure.
Brown paper and pva glue - when hit very hard hammer bounces without any damage but prolonged pressure leaves a bit of a dent.
Alternate layers of brown paper and newsprint - not as brittle and seems more resistant.

A most interesting topic.   I have had some limited experience making my own home made "composite" material using paste (both flour based and PVA based) with newspaper, old cotton T-shirt material, (my favorite) bed sheets and pillow cases that my wife is kind enough to save for me as they wear out. 

I have used them in combination with paper but not with each other.   I use cotton cloth when I need a light strong piece and I should say I have never made anything as big as an 8 foot long surfboard but smaller objects that fit in my hand.  I also made toadstool yard art that had been exposed outside to the elements for 3 of the 4 seasons going on the 3rd year. They are covered with 3 coats of Minwax Helmsmen Spar Urethane. The first coat went directly on to the finished but unpainted sculpt.  The remaining two coats went on last after the final painting was complete and dry.

I always mix in some acrylic paint in my paste and paper mache clay (used to replace some of the water) I read somewhere it adds water resistance to the mix and this has all worked well thus far.

I am always surprised at how strong and light these pieces are when made of the cotton cloth, paper strips and sometimes paper mache clay.  I have another thing I have not yet tried in my search for the "perfect" and even stronger home made composite and that is using fiberglass window screen mesh.   It comes in rolls like fabric, can be purchased in the large DIY stores and seems it could be used to make an exceptional composite material.  If anyone has used it or does try it I would very much like to know the results.

Bob C

Last edited by Pelletor (2011-05-06 18:36:09)