Tuesday, July 8, 2014

Carbonizing Wood: The Picnic Table

Several years ago I became aware of the origin of the blackness inside those half wood barrels you see for sale in garden centers.  The wood is charred to guard against decay.  Charcoal, it turns out, has very little to offer mold and fungus in the way of nutrition and so is very resistant to it.  What led to this understanding, for me, was seeing that a house and barn had been clad in charred wood, and that several wood product manufacturers now offer carbonized wood in various degrees of "cooked".  Being the curious guy I am, once I had a propane torch, I wanted to see how easy or difficult it was to master this technique.

First a word about the table.  It was built from salvaged wood using a pattern I found on the internet.  It's really quite simple and any search will turn up a number of patterns to chose from.  I chose one that fit the materials I had on hand, all scrap and salvage.  Only the lag bolts and screws needed to be purchased.

As you'll see in the video below, it's trivially easy to char wood.  With clean, stripped wood, just wave the flame of the torch back and forth over the surface until the desired level of char is achieved.

After the wood is charred I find that with the pine decking the loose soot is easily wiped off on your hands and clothes, so I removed this with a fine brass wire wheel attachment for my electric drill.  Just lightly running over the surface to remove the powdery char was all that was needed.  The remaining browned wood is still amazingly rich in color.

In Process - freshly washed after stripping

The final step involved using an old jug of "wet look sealer" from Baer.  I had thought to use it in the basement long ago but decided against it for some reason I can't recall.  It's water based and was still in good condition and the results on the charred wood are amazing.  I applied the first coat with a brush, the second with a sponge brush, and the third coat I just poured it into the cracks and crevices and smoothed it over with the foam brush to fill in as much of the irregularities in the surface as possible.  

Ready for Dinner - Blue hue reflecting the sky

The end result is quite impressive.  It came out much better than I had anticipated and I have to give the credit to the materials as the work was far too easy for me to consider this high craft-work.  See for yourself. If you decide to try the method on your own, make sure you use your torch in a well ventilated area and try not to set your wood on fire.  Small gouts of flame are going to be normal with resinous woods, but self-sustaining flames should be extinguished quickly.

Deep Grain
Update 7/19/2015:  I should have updated this post earlier this spring when the results of the Baer "wet look concrete sealer" surviving the winter were clear -where the sealer clearly failed to withstand the weather.  It did fine on surfaces that were vertical, eg. where the water she away, but on the top of the table, the portion upon which snow would sit and melt, the sealer failed almost 100%.  I'll be wire brushing the whole thing and will have to see if the carbonized look remains.  I'm going to try to get an oil based sealer or something that will take the weather better.