Hawthorne patio table in Process / by Ian Devenney

A little while ago I was walking with my mother at her cottage property outside of Kingston - a lovely spot.

 

Here's a shot of the pond, and another of my mother.

We were clearing some trails and I found a sapling with some really interesting texture. I have been interested in working with aluminum castings for some time now and it seemed like this sapling would be a perfect shape for some table legs. When I showed it to arborist Joseph Gillingham, he identified it at black hawthorne.

The casting process used for making the legs is aluminum sand-casting. In this process, sand with added binders is packed around the form or "plug" of the object one wants to create in metal up to a middle "parting line". Then, a release agent is put down and the other half of the plug is also packed in sand. Once the binders harden, the two sections are separated and the plug removed. When the two parts are re-assembled there is a hollow cavity into which the molten metal is poured.

In this case, I wanted an integral mounting plate as part of the casting, so I simply added a plate of 1/2" MDF to the bottom of the sapling, and filled in a hollow with bondo, an auto-body filler. The natural hollow could not be cast in sand, because it lay on the natural parting line of the plug.
The completed plug looks like this, with the finished casting beside it:

When the casting comes from the foundry (I use Skara foundry in Mississauga), it is still fairly rough, and the parting line can be seen in a thin line of protruding metal.
Finishing the castings is a labour-intensive job that involves removing the parting line and smoothing out the mounting plate with an angle grinder and a flap-disk.

Next, the casting is sand-blasted with 80 grit sand in a blasting cabinet attached to the air compressor.

Then, it is sanded by hand to polish the high spots, while still leaving the dull texture of the low spots.

In order to prevent corrosion over time, the legs were anodized clear. Aluminum doesn't really rust, but it does oxidize to a rough, dull grey colour. I wanted to keep the brightness of the polished areas and keep it easy to clean, so the anodizing step is crucial.

Unfortunately, in this case, the anodize tends to even out the tones of the leg, leaving it much more uniform than before. In order to bring out the texture of the wood grain and bark, I rubbed the legs down with a black India ink wash. It took a little bit of trial and error to get the mixture of ink to water right, but I think the overall effect is successful.

For the first iteration of the Hawthorne Series, I wanted to make a table with a stone top.

Granite and marble are probably the most commonly thought-of options, but they both have a hard, cold feeling to them. The aluminum legs are organic in shape, but the castings give the design enough "coolness" already. I knew I wanted a mostly black stone with grey accents to mirror the colour of the legs. Soapstone was the natural solution.

Many people think of soapstone as a grey, soft material used for carving. It is true that soapstone is softer than the other architectural stones, because of its high talc content but there are harder varieties in use for kitchen counter-tops etc. The upside of all this is that it has a luxuriously soft hand, and doesn't feel as cold to the touch as other stones do. And when oiled, it has a wonderful deep black colour. Unlike granite, soapstone is naturally non-porous, so it will never stain and sealing it is not necessary. If it does scratch, light sanding with mineral oil is all that is necessary. Ultimately, it will develop a patina, so it would not be the best choice for those who demand a pristine and flawless surface. Personally, though, I prefer the kind of elegance that patinated surfaces have. Wear and tear reads as an intentional aspect to the design, as opposed to "damage".

For a top to go with the Hawthorne legs, it seemed a perfect fit. The organic quality of the legs would do well with the elegance of worn-in soapstone.

So back to the constru
ction details, the stone is 1.25" thick, but still requires continuous support to make sure it won't crack. For the support, I used 1/4" thick stainless steel plate that was CNC plasma cut to reduce weight, to give a handle when moving the table, and to give an extra visual feature if one were to look underneath the table.

Future iterations of the Hawthorne table will feature cast-concrete tops, though I am happy to produce the design with any other kind of natural stone, too.