Recommendation? UV blocking finish?

E.Carlson

E.Carlson

Joined
Mar 28, 2016
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I have a request for a knife with a purple heart handle. Tried to sell them on kingwood but purple heart has sentiment for the customer. I know that it will fade from purple to brown with time, but is there a UV blocking finish that it suitable for knife handles?
Purple heart seems to finish nice enough on its own, so I was thinking a furniture wax like sun shield by Howard might help keep the color a bit longer.
Anyone use anything like this?
 
I make a uv resistant wax finish. In my testing it adds about 3-5 months to the oclor life of woods like purpleheart and paduak. Send me a message.
 
J. Doyle is right. Just make sure you follow the directions, especially the instructions about letting each coat of oil dry before applying the next one. I give it 24 hrs. between each coat and apply at least 8-10 coats. Since your scales are not in direct sunlight 100% of the time, that should give you about 15 yrs. Make sure you get a marine rated oil - your local marine supply or West Marine will have it.
 
joedhiggins said:
Teak oil, or Tung/Teak mix. Let it cure fully. If you want the best possible UV protection, put a coat of spar or other outdoor urethane on as well.

https://www.pcimag.com/articles/827...n-concept-for-indoor-and-outdoor-applications

I would also consider using a UV resistant dye of similar color to the wood.
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I do quite a bit of wood finishing for furniture and work with a number of different finishes and a word of caution here, first off dyes inherently fade with uv light you would need to put a good exterior spar varnish on top other wise all dyes will fade, secondly if if your going to use a spar/marine varnish skip the tung oil/ teak oil mix, the extra oil is redundant at best but at worst can effect how the varnish cures if the oil mix has not properly cured, cure time on a pure tung oil is minimum 30 days for just one coat if you do multiple coats especially on a dense wood like Purple Heart you are looking at a finishing nightmare trying to put a film finish on the surface.
 
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A tip for finishing Purple Heart and bringing out some purple, take a propane torch and slowly heat the surface it will bring out some more purple, you can then coat with a good exterior top coat with uv stabilizers and inhibitors in it, system three makes a good marine varnish that I would recommend or you can use a oil like teak oil or I’ve actually had better results using general finishes exterior oil, follow the instructions and have good ventilation cause these finishes have strong fumes, personally for a user knife I’d use the oil then when it eventually fades tell the client to resand with some 400 grit paper to freshen the surface and re oil the purple will come back
 
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Those of you who recommend spar varnish, doesn't that add it's own color to the finish which probably wouldn't look that great on purple heart.
 
Joshua Fisher said:
A tip for finishing Purple Heart and bringing out some purple, take a propane torch and slowly heat the surface it will bring out some more purple, you can then coat with a good exterior top coat with uv stabilizers and inhibitors in it, system three makes a good marine varnish that I would recommend or you can use a oil like teak oil or I’ve actually had better results using general finishes exterior oil, follow the instructions and have good ventilation cause these finishes have strong fumes, personally for a user knife I’d use the oil then when it eventually fades tell the client to resand with some 400 grit paper to freshen the surface and re oil the purple will come back
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I am with you, but I don't think the tung would hurt, but you definitely need a 30 day+ cure. The torch is a cool trick. If I am ever forced to work with purple heart in lieu of katalox or similar, I will give it a try. There are a few dies that seem to resist fading much better than the colorful exotics, but I have never tried them without a good finish on top, so I couldn't speak to their performance with just a coat of BLO or similar.
 
The tung oil won’t hurt but it’s not needed it won’t add anything once the spar varnish is over top plus you have a long curing time before you can top coat, if you break down a spar varnish to its base ingredients it already has more oil in it than a standard varnish or urethane to make it more flexible so oil underneath doesn’t do much. Also Golfer, Joe is correct a spar varnish won’t add any color that a coat of BLO wouldn’t add so no downside as far as color goes.
 
Looking at various brands of marine teak oil and it looks like they are all various concoctions of oils and finishes and UV blockers, not just a pure oil.
Sounds like it's already a mix of stuff.
 
Yes teak oil is just a marketing term, just a blend of oils a bit of resin and a lot of thinner, tung oil was mentioned in conjunction with teak oil, one could mix pure tung oil into a teak oil and depending on what blend of oils are already being used the pure tung oil will add a little resistance to water when compared to boiled linseed oil (which is what you normally will find as the oil component in a cheaper oil blend) a spar varnish is still a tougher finish than teak oil though, both are blends but the varnish will have more resin that forms a film and protects the surface and the teak oil has more oil making it easier to reapply but not as durable, anytime you are talking about wood finishes it’s best to be as clear as possible when talking about ingredients. If I told the average person to walk into a store and pick up a bottle of tung oil there is a 90% chance that I will not get tung oil. Finishing companies use terms like tung oil to label finishes that while it may have a bit of tung oil in it, it is not tung oil most of the time its a varnish labeled as tung oil finish, but that’s a bit off topic, if you find a teak oil that you want to try out if you can find out what oils they used then you could add ingredients to make a better finish, pure tung oil will give you more resistance to water and will also give you more time to work with the oil to wipe everything down, if you want to toughen it up add a bit of spar varnish to it, and if you want it to dry quicker add more thinners, most likely your average teak oil is going to be a mix of blo, mineral spirits and alkyd resin. Then they will add uv protection into that mix as well as probably a few other thinners in small amounts and maybe some more oils in small amounts. If you want to mix your own finish starting with a teak oil base as long as you match up thinner and resin components you will be fine, and you can add any oil that you want.
 
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Thanks, I was aware of the whole tung oil vs. tung oil "finish" issue, so when you were discussing teak oil, I wanted to be sure you were talking about the mixed product and not 100% teak oil, which I have yet to even find. I ordered some marine teak oil and I'll test it out on a small scrap before doing the knife. I have some spar urethane already.
 
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