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Polyurethane - downside??

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Forum topic by becikeja posted 12-16-2014 01:00 PM 1035 views 0 times favorited 17 replies Add to Favorites Watch
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becikeja

648 posts in 2281 days


12-16-2014 01:00 PM

As I read this forum, I see hundreds of finish protection processes. Do 1 coat of this, 1 coat of that, then finsih off with a coat of this. Or mix 2 parts this with 2parts that and apply 7 coats. You get the idea.

I have always just used a polyurethane. Now I will admidt I have tried several, oil based finishes, water based finishes, and the only one I will stand behind is the General FInishes oil based Urethane. It works for me.

But as I always strive to get better and better at my hobby. I have to ask? Am I missing something? Urethane seems so simple to apply, but so many have other processes and formulas. So there must be downsides that I have not considered.

So I ask the forum. What are the downsides to using a Polyurethane?

-- Don't outsmart your common sense


17 replies so far

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TheWoodenOyster

1275 posts in 1402 days


#1 posted 12-16-2014 01:29 PM

Honestly, I feel the exact same way as you. I have tried blends and pure oil and other stuff. Polyurethane is easy and looks good. What I don’t get are oil/varnish blends without a protective coat of poly over them. I understand using them to get the grain to pop out, but some people think Waterlox is waterproof. It ain’t. I suppose I could see using an oil/varnish blend for a decorative piece, but for a functional item, why wouldn’t you put poly over the top? My parents had a guy tell them to put Waterlox on their kitchen island because it was “Amazing”. Needless to say the island gets water spots and has to be refreshed once a year. Polyurethane is amazing. 2 part epoxy is amazing. Waterlox… not amazing.

So, I too am a polyurethane lover. Protection and ease of application.

I haven’t tried lacquer yet, so that could be a game-changer.

-- The Wood Is Your Oyster

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OSU55

1063 posts in 1457 days


#2 posted 12-16-2014 01:35 PM

I just used poly and the typical box store stains for 25 years. I decided I wanted to step up my game and create professional finishes on the pieces I spent so much time building.

Poly is still my favorite finish to own and least favorite to apply – depending on what I finish I want to end up with. If I want the “oil rubbed close to the grain” look, solvent satin poly is it (GF urethane is in this category), applied with a “dry brush” technique. Everything else is sprayed waterborne, usually lacquer or poly (I use Target Coatings products).

For higher film build finishes, solvent poly is a giant pita. It takes forever to dry, can be days between heavy coats. Because of the way solvent poly cures, you can get knit lines between the coats doing final sanding/rubbing out. Spraying it is a nightmare – the overspray doesn’t dry before landing and creates a sandpaper texture where it lands. The stuff looks great and is tough as nails, but a nightmare to use.

Pre Cat Lacquer is great for a lot of things, including blowing up yourself and shop. I didn’t want to invest in an explosion proof fan, so I experimented with waterborne finishes. I ended up with Target’s line of coatings.

I typically color the wood with dye stain, and use toner coats on top of that to get the effect I want (evens out the color and adds depth, or whatever effect I’m after), using shellac with Transtint dyes. The Target stain base WR4000 and the shellac pop the grain very well. Then apply the waterborne topcoat of choice. I can apply the entire finish in one day if I start early, give it a week to cure out, then sand/ rub out, wax. whatever I want to finish the piece.

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Blackbear

137 posts in 1687 days


#3 posted 12-16-2014 01:40 PM

I’m no expert for sure, but Urethane and Polyurethane are film finishes. They offer great protection, but if damaged are much harder to repair the finish. Usually you would have to sand the whole surface and reapply the film. Personally I would definitely use Poly on a surface such as a table top.

Oil/Varnish finishes do not offer as much protection but are very easy to repair scratches and dents that have damaged the finish, and in my opinion are much easier to apply than Polyurethane (except wipe on Poly is pretty easy too). I use an Oil/Varnish blend on many things like picture frames, cribbage boards, small toys, etc.

There are some great books all about finishes. I picked one up off Amazon from Bob Flexner called “Understanding Wood Finishing”, its a great read and very informative if your interested.

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Earlextech

1159 posts in 2158 days


#4 posted 12-16-2014 02:13 PM

Don’t mess with success!
I always tell people at my seminars that the reason there are so many finishes available is not because of such a variety of projects but more because there is such a variety of woodworker. My contention is that most woodworkers would be happy if they knew how to get a clear coat or stain and clear coat finish successfully, every time. Most of us will find the 5 finishes that work for us and then use them for the next 40 years. Only changing if the product goes away.
In my 25+years of custom woodworking I used the same 5 finishes the entire time. Occasionally going outside my comfort zone when a customer would challenge me. Thank you customers!

-- Sam Hamory - The project is never finished until its "Finished"!

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dhazelton

2326 posts in 1764 days


#5 posted 12-16-2014 02:28 PM

I use shellac because I can put down several coats with no lag time and once rubbed with 0000 steel wool and waxed it always looks gorgeous. Do what works for you. Doesn’t make you less of an artist if it doesn’t take ten steps and high dollar materials.

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CharlieM1958

16244 posts in 3686 days


#6 posted 12-16-2014 02:40 PM

I agree with sticking to what you like.

The differences between different types of finishes can be very subtle. For a combination of looks and durability, poly is hard to beat. For those who claim it it looks too much like plastic, I say that has a lot to do with how you apply it.

Sometimes the difference is as much about “feel” as about appearance. To me, nothing feels as good as an oil finish with a paste wax coating. But that wouldn’t be very practical for a piece that’s going to get heavy use.

I would encourage you to experiment, but don’t feel guilty about liking poly.

-- Charlie M. "Woodworking - patience = firewood"

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waho6o9

7179 posts in 2044 days


#7 posted 12-16-2014 02:56 PM

Excellent advice above.

If it’s not broke don’t fix it.

+1 for shellac and wax.

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wseand

2754 posts in 2509 days


#8 posted 12-16-2014 02:57 PM

They all give different results, differnt protections, different looks. None are the end all solutions. Dont get caught up in individual concoctions. You use a certain type of finish for a desired result. If you have a problem that is happening with a certain finish there are other routs to go. Some projects require a certain kind of finish or you are looking for a certain appearance. Get Charles Neil book or other books on finishing great reading. Finishing with differnt mediums can be challenging and fun.

Some say that water based finishes are the bees knees, I hate them and only use oil based. Wipe on varnishes come in a ton of species. Minwax poly is a well know all around great product, but there are 15 other types of poly_blends out there.

Have fun with it and dont get caught up in opinions, try a few out and see how they work for you. Because opinions are like A Hoes everyone smeels differently.

Bill

-- Bill - "Freedom flies in your heart like an Eagle" Audie Murphy

View Fred Hargis's profile

Fred Hargis

3950 posts in 1961 days


#9 posted 12-16-2014 02:57 PM

The urethane resins in varnish inhibit adhesion, hence the need to “scuff sand” between coats. Beyond that, I just don’t like the look; but if you have no problem with either of those it’s a very good finish. The urethane resins are also quite abrasion resistant which makes them perfect for floors. But once I discovered alkyd resin varnishes, I haven’t used polyanything in my shop. The alkyd resin formulas do not have the adhesion problems (no scuff sanding needed unless it’s to remove dust nibs) and to me eyes have a superior appearance. But they are very hard to fins, the only ones I can get are the SW Fast Dry Oil Varnish (a linseed oil formula) and P&L 38 (a soya oil formula, and my favorite). Even then, I really have to work to get the P&L product. I think the magic of using “poly” was greatly increased by Norm, since it seemed to be one of his favorites.

-- Our village hasn't lost it's idiot, he was elected to congress.

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JayT

4786 posts in 1678 days


#10 posted 12-16-2014 03:04 PM

The only real downside of Polyurethane for me is that sometimes I don’t want that plasticy looking finish on a project. If a piece is going to be handled a lot or exposed to any kind of moisture, I use poly. Danish oil and wax get used for most pieces that I want to avoid the poly film appearance. Occasionally, shellac and wax.

My next step if learning more about finishing is to start experimenting with dyes. Won’t change what I use for final protective coats, but I want to learn how to use dyes and stains in combination to achieve certain looks.

-- "Good judgement is the result of experience. A lot of experience is the result of poor judgement."

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OSU55

1063 posts in 1457 days


#11 posted 12-16-2014 04:38 PM

I agree with all the comments on gaining more knowledge about different stains, dyes, and finishes. Jeff Jewitt’s and Bob Flexnor’s books are excellent resources for explaining selection, types, methods, and problems with the complete finishing process. Get the latest editions from each. Intended use, desired look, and the wood type of the finished piece drive the type and method of finishing.

Shellac is an often overlooked finish. All of my “play pretties” (things that don’t get handled/abused) get shellac as well as shop made carts, jigs, etc. because it’s easy to work with and dries fast. It will prevent liquids from soaking into and dirt buildup on wood shop equipment items.

IMO, finishing is 50% of the project. Never trying something new (making or finishing a piece) is very limiting. One of the reasons I do woodworking is to learn various skills, try something new on the next project. Always doing the same thing over and over starts to sound like….....production work, not a hobby, but to each his own.

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ADHDan

800 posts in 1576 days


#12 posted 12-16-2014 06:01 PM

Quick question that seems to be on topic – what’s the practical difference between wipe-on poly and brush-on poly? For a few recent projects that didn’t require a picture perfect finish I just wiped on plain old Minwax poly from the BORG with old undershirt scraps, and they actually turned out pretty good. For a very small project (some coasters), it actually was much easier to wipe on the poly than it would have been to brush.

What’s the main reason not to wipe on regular poly? And relatedly, what should I add (and in what proportions) to turn regular poly into a wipe-on product?

-- Dan in Minneapolis, woodworking since 11/11.

View Fred Hargis's profile

Fred Hargis

3950 posts in 1961 days


#13 posted 12-16-2014 06:13 PM



Quick question that seems to be on topic – what s the practical difference between wipe-on poly and brush-on poly? For a few recent projects that didn t require a picture perfect finish I just wiped on plain old Minwax poly from the BORG with old undershirt scraps, and they actually turned out pretty good. For a very small project (some coasters), it actually was much easier to wipe on the poly than it would have been to brush.

What s the main reason not to wipe on regular poly? And relatedly, what should I add (and in what proportions) to turn regular poly into a wipe-on product?

- ADHDan

The only difference is the amount of thinner in the mix. If you look at the MSDS of most of the “wipe on” varnishes (and several other products that are really just a wiping varnish) you’ll see they often are 70% or so thinner. Make your own by thinning regular varnish 50/50.

-- Our village hasn't lost it's idiot, he was elected to congress.

View wseand's profile

wseand

2754 posts in 2509 days


#14 posted 12-16-2014 06:47 PM

You can add Mineral Spirits to the poly, I will mix a 60/40 or there about solution 40% being MS. You dont have to mix the whole can of Poly just what ever you need in a seperate can. I use a old mason jar or empty poly can so i can seal the unused portion.

-- Bill - "Freedom flies in your heart like an Eagle" Audie Murphy

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pintodeluxe

4859 posts in 2281 days


#15 posted 12-16-2014 07:10 PM

It’s fine if you like it, or have found a good brand. However the slow dry time on some poly finishes doesn’t work for me. I prefer to spray lacquer. Some people like to wipe on shellac. It runs the gamut I guess.
I will say that two coats of sprayed lacquer will build a thickness comparable to 5-6 coats of thin wipe-on products.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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