fred bartels’ musings

How to smooth a surface composed of irregular triangular faces like this?

It's a problem that I hope to solve using hard paper mache. If I can find a mache that hardens to the right consistency then I should be able to work up a smoothly curving surface by covering the triangles with a varying thickness parge of mache. This surface would need to be covered in turn with a waterproof layer of some kind; shingles or a monolithic membrane are both possibilities.

I've been using cellulose insulation for the paper ingredient of the mache experiments. I started with cellulose that uses ammonium sulfate as a fire retardent, and it produces a very strong and hard mache. There are some potential issues with ammonium sulfate however, so I'm also experimenting with cellulose that uses borate as a retardent. My first experiments with the borate cellulose were disappointing. The mache did not dry to the same hard consistency I've been obtaining with the ammonium sulfate cellulose. I'm continuing to experiment but suspect there may be something about the borate which interferes with the mix hardening and cohering. I recently mixed up identical batches of mache with the excepttion that each has only one of the cellulose varieties. The mixtures take about a week to dry fully so I should have a better sense by the end of April whether the borate cellulose will work.

I use 32 oz. plastic yogurt containers as my measuring unit. In the following ingredient list "cup" refers to one of these containers. The mix below seems to consistently produce a strong hard mache when using the ammonium sulfate cellulose.

1 cup industrial hemp fiber cut to 1" to 2" lengths (loose) *
1 cup cellulose (packed)
1 cup water
1/2 cup joint compound
1/2 cup saw dust
1" (in the cup) of wood glue

*I've also used cut up Phragmites tufts. which seem to work just fine.

Here's a picture of my laboratory. Very high tech.

To give you a sense of the strength of the mache I took this picture of a piece of mache bridging between 2x4s and supporting my full 200+ lbs.

In the next picture you can see the thickness of the mache piece in the image above.

A hard stable strong mache has many possible uses in building construction. I think of it as being almost like moldable wood. Definitely an interesting material with potential. If you are doing any experiments with hard mache, or would like more information about my experiments, please get in touch!