Wood Finish question - what did I do wrong

[tallgrass1951]

I made some stools/tables for my patio and the finish is turning yellow. I used Miniwax Helmsman Indoor/Outdoor Spar Urethane to finish the stools. They are made of hedge and the trees were down for over 5 years before I cut the slabs.

They have been outside since April/May of this year.

The can says it provides "Exceptional Protection From" Sunlight, Rain&Moisture, and Temperature Changes. Didn't say anything about turning yellow in the sun.

Did I use the wrong stuff?
What should I use?
How do I get this stuff off to redo them?

One stool in the pictures has been in full sun and the other has been in the shade.

 

[Motown]

It looks like the finish is breaking down from UV.I have come to the conclusion polyurathane just plain old *****. Maybe a product like Sikkens Cetol, or Sherwin Williams has a product also.

 

[Donzi camino]

I'm not a fan of spar urethane especially minwax brand, I prefer a true marine spar varnish. All oil based products usually amber or yellow in time. What I see in the picture on the left is the result of moisture under your finish. Sanding it back down to the wood or when all white finish is removed is required, than refinish 3 coats minimum.

 

[Kaizen]

Silken has held up great on my porch for ten years.


Sent from my iPhone using Tapatalk

 

[4xdog]

I tend to use acrylics on anything where long-term UV is concerned. It's one of the best polymers for ultraviolet resistance.

Urethanes may be more abrasion and wear resistant, but they don't have the exposure durability IMO.

 

[Skiff Builder]

Several checks in the grain probably letting water/moisture in, than wicking under your finish.
After sanding it down I would seal it with clear epoxy resin .Marine varnish for uv protection afterwards.

 

[Voi]

I made some stools/tables for my patio and the finish is turning yellow. I used Miniwax Helmsman Indoor/Outdoor Spar Urethane to finish the stools.

Last I checked Minwax made a Spar Urethane is both oil-based and water-based?

I assume you used the oil-based? It tend to cure amber.

I think you're also getting a natural darkening of the wood.

I'm out of the loop when it comes to wood finishing nowadays. VOC restrictions mean products have changed in the decades since I've used them.

 

[yeldogt]

you can't seal end grain -- the wood is moving and allowing water to enter -- the whole slab is wet and wet under the finish.

An epoxy product is typically used to delay this -- but it will eventually fail on end grain outside.

They way to do this is with an oil finish -- it will still turn but you scrape the surface and replace the oil. You need to use a true oil finish -- most things labeled as an oil finish are actually a modified varnish /// like Tung oil and will still make a skin that's got to be removed.

I made a few -- plane the top -- scrape and oil.

 

[dnschmidt]

Automotive clearcoat is the ultimate answer. I live in Arizona and anything I put outside has several coats of automotive clearcoat on it. Best UV protection available.

 

[gungatim]

I've found that minwax spar eurethane has very little UV protection. had a buddy use it on window frames in his home and after a few years even with low-e glass, it started degrading.

I would go with an epoxy as stated. I have used fiberglass resin with good results as well, it's what they use when making strip canoes (minus the fiberglass cloth, though a very thin cloth could actually be used and not be too noticeable).

 

[Voi]

I would go with an epoxy as stated. I have used fiberglass resin with good results as well, it's what they use when making strip canoes (minus the fiberglass cloth, though a very thin cloth could actually be used and not be too noticeable).

For sun exposure I'd be inclined to go with polyester or vinyl ester resin instead of epoxy. I'd have to do some catch up reading to see which of the two would be more UV resistant and/or flexible given that this is a slab with mostly end grain exposed.

Last time I used US Composites they had a really good customer service tech answer some questions about a specific product/use I had.

As I recall their surfboard resin is the water clear and their most flexible and UV resistant of their polyesters but I'm not sure how that compares to vinyl ester.

 

[tallgrass1951]

I appreciate all of the suggestions. I just want something that will keep the wood from turning gray. The hedge is not going to rot, we have posts that have been in the ground since the 50's that have not rotted, but like all wood it weathers if left unprotected.

 

[Colin Len]

I tried that SPAR stuff before and it was terrible. Says it's good for UV but not in my experience. I haven't done a lot of work with these types of products but after the research I did for my bench top and some outdoor redwood planters I, personally, would stay away from anything like that which builds up, can yellow and needs to be removed in order to refinish.

I've used Penofin on some outdoor planters and posts and am really liking the results. You don't get a gloss finish or even a coating and yes, it will grey a little over time. But, when it does just give it a light sanding and re-apply (and really I think you wouldn't even need to sand it in some instances).

 

[ford33]

Remove the old finish and put a "drying oil" finish. Boiled linseed oil is often used for outdoor wood. This finish will soak into the wood fibers and protect the wood. It lasts only one year but provides a greater protection to the wood. It soaks into the versus coating the wood.

A film finish such as polyurethane may appear to last longer but it does not. The film is hard and will crack allowing water in and the wood will expand cracking more of the hard film finish. Eventually you have little protection under the film finish and it will be necessary to remove the hard film before applying more to "protect" the wood.

Just realize that outdoor wood items require maintenance and it is much easier to wipe on linseed oil every year than sanding and reapplying a hard coat finish.

 

[gungatim]

I appreciate all of the suggestions. I just want something that will keep the wood from turning gray. The hedge is not going to rot, we have posts that have been in the ground since the 50's that have not rotted, but like all wood it weathers if left unprotected.

in that case you should stain it before the varnish. all wood will age and change color, some more than others. you may need a sealer before the stain as well.