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Tuesday, 9 August 2016

Vacuum chamber & stabilised redwood burr

Vacuum chamber & stabilised redwood burr 

I have been using a homemade steel vacuum chamber to stabilise soft and punky woods for a couple of years now

Metal vacuum chamber

Although it works OK trying to see what is happening by looking down onto the surface of the resin is difficult.

I buy and use Cactus juice stabilising resin from Turntex woodworks in Texas, USA and decided to take the plunge and buy a chamber too.

Chamber from Turntex woodworks.
I had some really highly figured redwood burr that I wanted to use to make turned boxes with but I knew from past experience that the burr is too soft to cut cleanly without stabilising.

highly figured redwood burr
The burr was covered in wax and wet when I bought it so I roughed out one piece in April 2016 and set about slowly drying it as to stabilise wood the wood must be bone dry

I had the burr ready by late July so I put it and a few other pieces into the chamber

First batch in the new chamber before adding resin

I had a new batch of cactus juice so I added 3/4 of a US gallon into the chamber. 

Initial forming of air bubbles

When you first pull vacuum you the air bubbles coming from the wood can be extreme and can rise up the chamber towards the lid and can enter the tube leading to your pump if your not careful!! so you have to control this with a bleed valve and then after a the first few minutes you can shut the valve and be at full vacuum.

the advantage of the clear chamber is being able to control & monitor the process

  You can see the air being pulled from the redwood burr blank

 After 3 hours of vacuum being pulled the air bubbles stopped, (the time under vacuum varies) 
If there is any moisture in the wood you will get small champagne type bubbles and they will take hours and hours to stop so it is really important that the wood is bone dry
I put a piece of masking tape onto the resin level before releasing vacuum.

The resin needs to be at least an inch above the surface of the wood before you release vacuum if the wood becomes uncovered in the initial release of vacuum it draws air back into it and you have to start all over again.

26mm change 
One minute after releasing vacuum the resin had dropped by 26mm

Normally you leave the wood in soak overnight then cure it the next day but i was advised that redwood benefits from a longer soak so I left everything in the chamber for 1 week

31mm change

After 3 days the resin level stopped dropping and stayed 31mm away from where it started.

here you can see some before and after pictures showing the weight increase and the figure in the redwood burr blank once it had been cleaned up.
redwood burr before stabilising

walnut before stabilising

redwood burr after stabilising

walnut after stabilising

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