Pine Pitch Tests

Tim Lovett  April 05 | Home | Menu

What is pine pitch like?

Genesis 6:14 "...and cover it inside and outside with pitch."

No need to paint Noah's Ark black - the pitch was probably extracted from pine trees (which might be "gopher wood" anyway). Perfectly water proof, gum based pitch melts easily, has a faint pine odor, looks like a thick varnish, washes up with alcohol and remains flexible. It can be used as both a coating and an adhesive. It could be applied either with heat or by dilution with alcohol. Manufacture is simple. Surely this is the perfect material, even by today's standards.

 

Like a thick varnish: Natural pine tar pitch applied to bare wood. Image Tim Lovett 2005

Applying the pitch

The sample above was applied by heating the pitch over a flame. The pitch is similar to candle wax, but tougher and melts at a higher temperature. Unlike wax, the pitch does not exhibit a sharp melting point, but softens gradually with increasing temperature (like honey). This makes it easy to work since the cooling pitch takes some minutes to harden, even after it cools. Viscosity is quite low when hot, similar to paint.

The appearance of the pitch coated wood is similar to a high gloss polyurethane - very clear with a hint of amber. However the slightly tacky surface would not hold a gloss on a wear surface such as a floor. The advantage however, is that the pitch should make the decks a non-slip surface - even when wet. Rosin is used to make violin bow "grip" but not "stick", exactly what you want when walking on a deck in heavy seas.

Anyone who has climbed a pine tree will know pine gum is not easy to clean off your hands. It is waterproof and doesn't respond to soap either. I washed it off with methylated spirit (methanol) quite easily, so it should dissolve in strong alcohol (ethanol). 

Flammability does not appear to be a problem, although it would be a risk once a fire took hold. In a naked flame the pitch melts like a candle but the flame extinguishes when removed from the flame, This means the pitch could be applied by pouring from a cooking pot, spread out with a hot iron and, if desired, glossed using a torch flame. 

Alternatively, using alcohol as a solvent, a much thinner coating of pitch could be applied - especially for interior woodwork. Genesis 9:21 gives ample evidence of Noah's ability to make alcohol..

Properties

Waterproofing

Most readers would assume the pitch was to meant waterproof the Ark. This has been practiced since antiquity, and tree resin has been the dominant source. 

Waterproof: Pitch coating acts as a water barrier. Image Tim Lovett 2005

Preservative

Waterproofing also has a preserving effect, not that preservation is needed when the voyage lasts four to five months. Perhaps the construction period was quite long and preservation was needed on exposed woodwork.

Adhesive

The adhesive performance of the pitch will be very sensitive to the quality of resin, extraction process and how it is prepared. Rosin based adhesives are a large part of modern application, but a starting point the mechanical properties of simple brewer's pitch will be studied.


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