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Tuesday, 25 March 2014

Stabilised burr horse chestnut - Hybrid box blanks

As I mentioned on my previous blog post here are some hybrid box blanks that i have cast using the stabilised burr horse chestnut.

 To buy these blanks and many others please visit my website

Monday, 24 March 2014

Stabilising wood

Hello folks

I went to one of my tree surgeons yards recently and there was a big horse chestnut trunk with lots of burrs dotted all over it.

The trunk was about 30" wide which is a bit big for me to tackle on my own so I cut the end of the log to see if the wood was worth bothering with. It had gone soft and really punky so i decided to just cut two of the biggest burr's off and see if they had stayed a bit firmer.

When I got them home I removed the bark and power washed them, waited a few days for them to dry and then cut them on them on the bandnsaw.

The wood was really pretty with a mixture of burr figure with some area's of spalting, but it was too soft, in fact in places it was so soft you could sink your finger into it!! I cut most of it box blanks and I cut the spiky natural edge for hybrid blanks.

I went back to the yard a few weeks later and collected the remaining burr's

I wouldn't normally have bothered with this type of wood but I could see that it was special and knew a little bit about a technique to stabilise the wood which would allow me to use it.

After allot of reading and google'ing I bought some Cactus juice stabilising resin from Turntex woodworks in the US and while it was on its way to me I set about making a vacum chamber.

I already had a vacum pump which I use on a vacum chucking system on my lathe and decided to build an acrylic chamber from a 5mm thick tube and 10mm thick top and bottom. I drilled the top and tapped it for a simple dry vacum gauge and 10mm connector and bleed valve.

To stabilise wood it needs to be as dry as possible, the natural edge pieces that I had cut didn't take too long to dry as the wood was very soft, I got them down to 5/6% MC.

I loaded up the chamber with 6 pieces and found an old backing plate to weight them down, poured in the resin and started to pull a vacum. For the first few minutes I had to control the bleed valve so that the bubbles didn't rise up too far and get sucked into the pump ( I will get around to fitting a catch pot in case this ever happens) once those first few minutes are over the bubbles settle down and you can get on with something else.

A short video clip

After about twenty minutes I noticed some hairline cracks

I quickly released the vacum and get the resin out, just in time as the tube fell apart

The plastic had changed, it was really brittle and felt odd to touch, i spoke to the tube supplier who told me that active ingredient in the resin Methacrylate esters is the only thing he knows of that would have reacted with the tube and changed its composition!! (sod's law)

Not to be out done I visited a welder friend and he made me up a metal chamber of roughly the same size

It works great but doesn't look as pretty!! its a bit tricky to control the bubbles as you are looking down through a little window in the top but with a little practice it can be done.

I have now successfully stabilised 20 or so natural edge pieces, on average the wood gained 250% in weight which is a great result and I have now cast some of  them into hybrid blanks over the past few days. I will post some pictures of the blanks soon.