Keeping Purpleheart Purple?

[woodpig]

I bought a small lump to turn some boxes. Any recommendations on finishing to keep it Purple once turned?

 

[Kalimna]

This crops up every so often on the luthiery forums, and the replies seem to fall into 2 camps. 1) Eventually the purple will turn a very dark brown, and 2) The best way of slowing this is to finish with a UV resistant finish.

Cheers,
Adam

 

[woodpig]

Thanks, sounds consistent with what I've read elsewhere.

 

[sploo]

All I've done in the past (mostly jewellery boxes) is use shellac sanding sealer followed by furniture wax. Some items are >10 years old, and still a nice strong shade of purple. The don't tend to sit anywhere that bright though.

 

[Eric The Viking]

There was a debate on 'ere some years back. 'S my fault, I think, in that I asked the question, too.

I left a pile of Purpleheart shavings on some white kitchen roll on a double-glazed-but-sunny windowsill. They quickly went brown. I have two small slabs of the stuff left in the workshop (main use: holding sheets of wet+dry flat in the drawer). They are still purple-black, but they're kept in the dark all the time and mostly stay cool too. They make that whole drawer smell as though something died in it, and that's hard because it's a metal drawer...

... Did I mention that it smells vile? It goes black (or the sap does) when you cross-cut it. The mineral inclusions blunt tools very fast. The splinters are downright evil.

In Lincoln's book, "World Woods in Colour", uses are described as "heavy outdoor constructional work, bridge building, fresh water piling, dock work, cladding, house construction and vats", in other words you hammer it into mud, and it doesn't rot, nor break when ships thump into it, and boring worms break their teeth on it.

Sounds about right to me. All else is insanity.

E.

PS: Being more serious for a moment, Lincoln mentions that it "...exudes gummy resin when heated by cutters," and that spirit finishes remove the colour and lacquer finishes preserve the colour. I've proven the spirit thing (try it with meths!), and the gummy resin, which turns the cut completely black and causes alarming smoke even with a newly sharpened TS blade.

 

[Woodmonkey]

I made a pot pouri bowl for my mum at least 6 or 7 years ago which has been sat on her sunny bathroom window sill and is still a nice deep shade of purple I think I used shellac and wax. I also made a bed from it last year which I used finishing oil on and AFAIK is still looking good

 

[Alexam]

Recently been using purpleheart and find that Tru-Oil is very good and seems to retain the colour better than shelac and wax.

Both of these boxes have had three coats of Tru-Oil and were not shelac sealed first.

Alex

 

[Eric The Viking]

Those look rather nice, Alex!

 

[woodpig]

Yes, very nice work on the boxes!

Where did you get your Tru- Oil, is it the stuff used on gun stocks?

 

[Alexam]

Yes Pete, that's the stuff. I only ordered an 8 oz bottle, as i'ts fairly expensive but it goes a long way putting it on with a cloth pad and leaving 24 hours between coats.

http://www.amazon.co.uk/Birchwood-Casey ... ds=tru-oil

 

[marcros]

unless you are using tru-oil every day, don't be tempted by the 32oz bottle that they do- it does go off over time and as alex says, a few drops go a long way. Even if you do use it every day, I would still stick with the 8oz bottle, and replenish your stock more regularly. When I open it, I puncture the foil cover under the lid rather than remove it- same with hard wax oil and any similar finishes- it reduces the exposure to the air. I also immediately decant some into another container on most oil finishes, although I haven't on tru-oil.

I tend to put a few drops on the wood, rub it in well working an area a little smaller than the size of your palm, in circular patterns. Then by the time that you have completed that coat on something, start from the beginning. After 3 or 4 coats, i would leave it for a while- 24 hours ideally, but at least overnight. You adjust the number of drops to the area that you are working, it becomes obvious how much you need. I tend to do these things at the same time of day, so it tends to be close to 24 hours- i.e. after dinner each night because I am at work during the day.

 

[Eric The Viking]

Back in the days of chemical photography, we used to buy 'concertina' bottles to keep developer in. It was more important with colour developer to keep as much air out as possible, IIRC (but I last processed a roll of E6 about 20 years ago).

Anyway, they were expensive, and I've heard of people inflating plastic bags inside ordinary bottles, dropping marbles in, and so on, all to reduce the air space above the liquid.

It would be good to know if anyone has a similar trick for glues and finishes...