Natural Waterproofing (Continued)

Last week, we joined Abari in Narayangarh, Nepal, to conduct further experiments for natural waterproofing.

In our prior experiment, part of the shingles we had used were, accidentally, not treated against fungus. Besides, we had doubts as to what factors exactly had caused the decay of the waterproofing materials. The resins could have decayed because of fungus, water, UV or intermittent temperature variations causing the samples to expand and retract. Moreover,  we had not taken exact measurements of the water content of the coated bamboo, before and after exposure, nor did we compare our natural coatings with industrially produced ones.

In last week’s experiments, we tried to mend these deficiencies by adding more control over the various factors that affected our samples. Hence we cut out 15 pairs of 1 inch square bamboo pieces, each treated with a different medium, including one untreated set. From each set we exposed one sample to normal outdoor conditions whilst we placed the other in a small jar filled with water. Among the 14 treatment media, some were industrially produced (starred in the list below):

  1. Gum arabic diluted with ethanol,
  2. Liquid silicone,*
  3. Liquid silicone diluted with water (1/3),*
  4. Black Japan,*
  5. Shellac diluted with ethanol,
  6. Sal resin diluted with turpentine,
  7. Melted shellac,
  8. Melted gum arabic,
  9. Sealer (commercial product),*
  10. Charred bamboo (bamboo “fried” in oil or wax),
  11. Bee’s wax,
  12. Linseed oil overlay,
  13. Linseed oil injected with Boucherie pump,
  14. Smoked bamboo (consisting in slowly smoking green bamboo over low fire).

We measured the moisture content of the bamboo before exposure at 15%. In few weeks we shall take a look again at the samples and measure moisture content again and compare.

With this experiment we hope to find an acceptable waterproofing medium. Even if the medium isn’t perfect (we don’t hope any of the pieces pickling in water to come out with the exact same 15% moisture content), it should refrain water impregnation significantly. Moreover, we focused on exterior (rather aggressive) exposure in this experiment, but our waterproofing media could very well work in more friendly (indoor) conditions. Here we are pushing the media to their limits. We should also consider that waterproofing is not only a matter of coating, protection against water should mostly be done by design. reducing the exposure to the bare minimum. In the future, we will also try some waterproofing media on rammed earth and mud plasters.

Prior to conducting this experiment we tried out few other coating media, notably by mixing some together. For instance, gum arabic seemed to be to brittle on its own and bee’s wax too soft. By adding a little was to the gum arabic, we could create a more elastic coating. However, it didn’t seem to hold well under the scorching sunlight. We also tried to apply molasses, as seen on few Internet videos, but that simply didn’t hold onto the bamboo.

We could have increased factor control over our experiment, by exposing samples to UV only or temperature variation only etc. but that would have been excessive. What we really are interested in, is whether or not we can waterproof.

We will give more updates on the results of our experiment in the future.

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