I installed a t&g cypress ceiling in my new sunroom. I want to keep the natural color, so I’m looking at a clear water-base satin finish for it. What is the difference between acrylic & polyurethane? It will not be getting any direct sunlight, but a lot of indirect light & high humidity here in <!—-><!—-> <!—->Florida<!—-> <!—->, so do I need UV protection? Any suggestion on brands?
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Sorry I can't be of much help, but I did check through my Taunton finishing guide for some info. Didn't find any definitive difference between acrylic or polyurethane other than one is acrylic resin, the other is...
Water-based is generally preferred to prevent darkening of natural wood, and I did find a reference saying acrylic fares better for overall durability. Some info on the Deft website leads me to think that the crosslinking of molecules, which could result in the difference in performance between the two, is a big factor.
You might search the Taunton site for the subject; I'm sure it will bring up some articles if you don't get a response here. I've also found the Sherwin Williams site to be a good source for info. If you're so inclined, as I am, you can read the specs on each product and see what conclusions you can draw.
This will at least bump the discussion back up, so you may get additional responses that will be of more help.
It depends on what you are calling polyurethane. It's become more a marketing term I guess.
traditionally polyurethane is a varnish with a urethane resin mixed in. Most varnishes today are oil based.
water based finishes dry by evaporation, like most lacquers except the solvent is of course water. Some of these water based products have urethane in them usually modified with acrylics.
Then there are the "water based" products that modified or cross linked with urethanes and/ or other oil type resins.
The urethane contributes a toughness that makes it more scratch resistant, which is probably not needed in a ceiling.
If by UV resistant you mean yellowing or ambering most finishes will amber or yellow with direct and indirect light. If you are looking for a non yellowing finish acrylics or modified acrylics are your best bet.
Most interior finishes do not have UV blocking capabilities, there maybe some exterior finishes better suited for that purpose. A lot of them are tinted to some degree. Might try googling for log cabin finishes or exteior wood finishes
See http://www.sikkens.com
Click on Decorative Coatings.
Click on USA.
Click on English.
Click on Interior.
And you are on your way.
I love their products.
JohnG
oil based polyurethanes will add a bit of amber to the color so stick with water based acrylics to keep the color as is. If you go with the oil based finish be aware that various brands differ in their color and the difference can be dramatic.
Kelly moore makes a water based poly finish (Kelthane) that is easy to apply with brush or sprayer and smooths out great. It's $100/gal, but worth it. There are probably other good finishes, but this one works better than others I've tried so it's my go-to finish.
If using a semi gloss or matte make sure to stir the pot as you go not just at the beginning or where you start will be more dull than the end as the dulling agent settles to the bottom. Gloss doesn't need to be stirred at all.
Best of luck!
Beer was created so carpenters wouldn't rule the world.