Toughest, Repairable Exterior Hardwood Finish

[gerryv]

This might be of interest to some others here as well. Any recommendations?

Cost is not really a factor in terms of the finish. Suitability and durability are.

We've been asked if we could produce a small collection of exterior hardwood furniture that has a premium (vs. rustic) look. The wood/grain must be "classy." The species has not been defined but will likely include a few suitable ones. It will incorporate 3D carving.

There are a few catches however...
- It must stand up to heavy usage incl. a lot of bumps and abrasion so the finish must also be spot repairable. That would include localized sanding and brush/rub-on repair by the owners and the repairs must blend in very well.
- A degree of sheen is wanted rather than a flat look, including after spot repair.
- The finish needs to be clear with minimal yellowing expected.
- The finish should not peel or crack.
- It needs to be UV resistant and could see both strong summer sun and likely also unprotected winter exposure.

I was thinking a high grade spar varnish but I'm reading that while spar varnish was initially developed for maximum "mechanical" toughness and crack resistance, that requirement is now largely ignored with priority very much on looks only. Are any of these more durable than others or perhaps something better?

[coryatjohn]

Sounds like a UV cured finish would do the trick. These take extra equipment but if cost isn't an impediment, it might be what you're looking for.

[jTr]

Epifanes marine gloss varnish. I'm starting to sound like a broken record, but I've tried lots of oils, spars and magic epoxy primers, and paid the price in labor to re-work. Go to website and follow directions to a "T". Re-touching is as simple as a quick scuff sanding and a few licks of the product.

This product meets all your requirements, and needs no expensive curing equipment. You may use a high quality brush, but if you can spray, it will look as though you dipped the item in epoxy bar top coating. (In fact, I've repaired someone's failed attempt with that epoxy flood coat by sanding and spraying epifanes over the top - worked perfectly).

Six coats are recommended - don't skimp. If sprayed, you'll need to maintain about a 30% thinner amount - I've used mineral spirits for spray thinning, but acetone sets up a tack /skin a bit quicker. Either way, you'll need a week to do this - 24 hour cure and 180-220 grit scuff are required between coats.

Avoid oily exotic woods if you have a choice - they're gorgeous (see ipe furniture photos below), but the oils seem to loosen the varnish's bond a bit quicker. The stools are pine, and have held the finish much better.

Jeff

[coryatjohn]

>> If sprayed, you'll need to maintain about a 30% thinner amount - I've used mineral spirits for spray thinning, but acetone...

Ouch! That's a lot of stinky chemicals!

[bleeth]

Sikkens Cetol has an exterior gloss topcoat product for marine use that is very good. Ease of spot repair is one of it's strong points as well as UV resistance.
I've used it on Boats both for Teak (Oily stuff) and Mahogany and never had a complaint. Doesn't flake or bubble over time as most Spar Varnish will and is a heck of a lot easier to prep for maintainence coats later.

Not knocking Epifanes-that is a good product as well. I just like Sikkens better.

[gerryv]

Really appreciate the feedback so far and I DO appreciate the reality checks I'm getting here as well as on the Jamie Oxenham and Shopbot forums where I've cross posted in case the topic is of interest to others. Thanks :D

A bit more info. I called the potential client and explained the conflicting requirements and his response was kind of predictable... tell me what you "can" do. That got us to what the priorities were so it comes down to these.
- Must be repairable by client without special finishing skills
- Annual touchups okay but longer would be nice
- Doesn't have to be semi or high gloss but definitely not "flatish"
- Should bring out the beauty of the grain and create a rich look
- Added cost associated with long cycle times due to numerous coats with long drying times could not be absorbed
His final comment was: What do the guys that build high quality park and bus stop benches use?

It turns out he wants to offer a narrow line of personalized (CNC carved) benches to museums, corporate & condo gardens, etc. I'm guessing that this could be an interesting niche for others as well considering the growth in corporate thinking gardens, premium condo rooftop gardens, etc. Heck, maybe even themed subway stations (chuckle).

Does this help us narrow down what might be the best compromise?

P.s. Dave, I appreciate your CETOL suggestion as it could well turn out to be a practical and efficient "can do" compromise approach, considering their clarified needs/wants are.

[gerryv]

John, yes the UV aspect is important. It seems it's more a question of maintenance cycles vs. cost. I am getting the sense that because there will be a lot of bumps and abrasion, that may require annual or bi-annual repairs so outweigh really long term UV resistance. Then again I'm not in Arizona either so may not appreciate the latter enough.

[coryatjohn]

John, yes the UV aspect is important. It seems it's more a question of maintenance cycles vs. cost. I am getting the sense that because there will be a lot of bumps and abrasion, that may require annual or bi-annual repairs so outweigh really long term UV resistance. Then again I'm not in Arizona either so may not appreciate the latter enough.

I was talking about UV cured finishes. They go on as a liquid and are cured solid in seconds using a lamp. The finish is amazingly tough. For maintenance, field repairs can be done in minutes with no drying time.

There is an upfront cost that's considerable for the lamp so it's probably not an option anyway.

Here's a link to a supplier of lamps:

http://www.americanultraviolet.com/uv-curing-solutions/surface-curing-porta-cure.cfml

[bleeth]

The additional information you have supplied only reinforces Sikkens as your choice. On something like park benches a maintenance man with "jack of all and master of none" skills could do the annual or so re-coat easily and the products are readily available as well as having a long shelf life.

[Ajcoholic]

I havent found a better exterior finish than Sikkens... withstands the tough winters here, and summers too.

[danhamm]

Aye, my vote goes with Sikkens also, it may not be a clear cote but it still maintains the grains.
And where there is direct weather contact is it easily redone.

[denmanmarine]

We use Awlwood (http://www.awlgrip.com/products/varnishes/awlwood-ma.aspx)for all our exterior marine applications. Good for a number of years and is easy to apply. Moisture curing, 3-4 coats per day and hard to sand the next morning even in lower temps. Easy to spot retouch too.

[khaos]

Purpleheart is awesome outdoors. It turns a great grey color. Its VERY dense and has a tight grain making it durable. A few old benches in some NY parks use purpleheart and it is strong.

My 2cents

http://www.finest1.com/benches/grandcen.jpg