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 Post subject: Finishing purple heart?
PostPosted: Fri Apr 02, 2010 11:57 pm 
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I am turning some purple heart.
Tried several oil based finishes and the wood went from purple to a brown colour.
What can I use on purple heart to maintain the colour.

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PostPosted: Sat Apr 03, 2010 12:09 am 
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Hey Monte,

You will need something that blocks the UV, that's what causes the color change.

Tom

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PostPosted: Sat Apr 03, 2010 6:22 am 
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tms wrote:
You will need something that blocks the UV, that's what causes the color change.


Most important, display the piece out of the sunlight. That, plus a spar or similar UV-resistant varnish will hold the color the longest. Won't stop the degrade, but will slow it.


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PostPosted: Sat Apr 03, 2010 10:06 am 
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I've also noticed in the few times I've turned purpleheart I have to be very carefull not to heat it up while turning (with either the tool or sandpaper) or it browns very (very) quickly. In addition, some finishes will evidently turn it brown right away.... I haven't had this happen so I don't know.... I believe I last successfully used a wax/shellac friction finish.

Lawrence


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 Post subject:
PostPosted: Sat Apr 03, 2010 11:22 am 
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tms wrote:
Hey Monte,

You will need something that blocks the UV, that's what causes the color change.

Tom


The wood turns brown as soon as the finish is applied. I have used Danish oil, oil based poly, and lacquer.

UV is not going to be a real problem as it is for pens.

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PostPosted: Sat Apr 03, 2010 12:27 pm 
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Hey Monte,

The UV causes the browning by oxidation. Other things that accelerate oxidation are heat, and exposure to pro oxidants such as metals and rancid oils. If you are making pens, perhaps the heat generated from sanding on the lathe is promoting the oxidation of the wood.

Tom

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PostPosted: Sat Apr 03, 2010 4:22 pm 
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Purple heart is so dense and full of silica that it really doesn't need a finish at all. Just polish it with 1000 grit or higher and a little wax.

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PostPosted: Sat Apr 03, 2010 10:21 pm 
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I haven't figured out what makes PH turn Purple except time. When I sawed some the fresh cuts were brown, within 2 weeks of sitting in the shop it turned purple.
I finished it with 2 coats Zinsser Bulls Eye shellac, then 2 coats Minwax water based poly.
5 weeks ago I set the piece on the front seat of the car, so it would be in the sun 4-6 hours everyday. It's still nice and purple so I don't know if the sun will fade it.
Maybe I'm not much help, buit it sure is pretty wood.


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PostPosted: Sun Apr 04, 2010 4:46 am 
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I have also found that PH changes back to purple after cutting it. I finished it with danish oil and then a few coats of wax and it has remained beautiful for a few years now.
Joe


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PostPosted: Tue Apr 06, 2010 8:03 am 
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I used a plain ol water base and "toxic" clear finishes works great .

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