Pros and Cons of Waterborne Finishes

      Here's a long discussion of reasons to prefer waterborne finishes (or not). March 29, 2008

Question
I'm thinking about switching to water based finishes. Besides the health issue, what are other advantages or disadvantages? Are the finishes just as good as solvent based? I never used them, but I think it is the future and I would like to at least give it a try.

Forum Responses
(Finishing Forum)
From contributor J:
Another advantage is not having to use solvents to clean out your equipment after spraying. Just a little warm water to flush your gear and you're done. Also not having to worry about flammability is certainly a good thing. I'm not sure there is a big difference in health concerns, though, as WB finishes are still hazardous to breathe. You'll still need to have a spray booth of some sort, and use a quality mask while spraying.

As far as quality, there are so many finishes available nowadays that you should be able to find something sufficient to meet your needs. Just like with solvents there are many different finishes to accomplish different things. I use products from ML Campbell and Target Coatings and some are very good.

Take a look at the Target Coatings website, as there is a wealth of information there. Do a little research and most importantly, practice on scrap for a while before attempting to use WB on a job. It behaves a little differently than SB in my experience, so you have to get used to it.



From contributor X:
Pros:
- Non-hazardous
- Lower commercial insurance
- No fire suppression
- Lower VOC emissions
- Better for employee health
- Easier storage
- No solvent for cleanups
- Easier to strip or repair

Cons:
- Requires heat to dry fast
- Cures clower
- Not as durable in some cases
- More labour sanding
- Much harder to sell (to solvent fanatics)

Overall the WB will cost a bit more to apply, but it's easier and better for the environment. Recently all the automotive body shops in my area switched to WB and they all started advertising it. This has made a lot of the cabinet guys stop in and take a second look at my finishes. You can't tell the solvent from the WB unless they are both sprayed on the same panel. It's important to sell the WB finishes for what they are and let the consumer make the environmentally responsible choice.



From contributor A:
Contributor X, I've used SB finishes, switched to WB, and then back to SB. I do a lot of pigmented (paint) finishes, and have had difficulty finding a pigmented WB product with which I can obtain a uniform matte sheen, and which is as durable as pigmented CV, and gives the beautiful, smooth, uniform matte finish that pigmented CV does. Have you found a pigmented WB product which is a good substitute for pigmented CV and/or 2k poly? I'm on the fence regarding transparent SB and WB finishes. I can get similar results with either, but generally find the SB finishes (CV and 2K poly) to be more durable, but much more difficult to repair or maintain.


From contributor S:
Some here consider me to be a waterborne hater, but I'm truly not. My problem with them is that the ones I've tried don't get hard fast enough. I'm a 2K acrylic urethane freak and spoiled by automotive clear coat which is hard as glass and as flexible as plastic. I've not found anything to equal 2K acrylic urethane... Maybe someday.


From contributor X:
I don't think there are any pre-cat solutions in WB or SB that will compare to a 2k urethane. However, there are a number of waterborne 2k urethanes and some 3k urethanes that will provide the same chemical and abrasion resistance. These are used in the automotive industry.

Why exactly would you use a 2k on a kitchen or furniture anyway? Nitro and CV work just fine for cabinets and case goods. Target's EM9300 poly carbonate urethane works well for pigmented colours and for flat finishes at 15 degrees. Nice and smooth off the gun, good build and quite durable. If you don't have heat it takes 3-5 days to cure and if you add heat to 75F+ it cures in 72 hours or less. If you have a really good booth with heated air and an IR bake cycle, you can cure in 4-8 hours.

I use the USL pigmented to the colour I want and then clear coat with the 9300 flat for durability. The most expensive con on WB coatings is the heated air makeup in the winter. Thankfully natural gas is cheap.

If you want to spend the money on waterborne 2k urethanes, they are every bit as good as the SB 2k. This is why all the automotive stuff is 2k base coat, 2k colour coat and 2k or 3k clear coat and now all waterborne.



From contributor E:
Contributor X, when you discuss 2k water base urethanes, are you talking about car paint? They are pretty pricey. Is there a company that sells 2k urethanes other than car paint companies?


From contributor U:
One of the features I like the most is if/when I get a run, all I have to do is use a damp rag! Wipe away the run and immediately re-spray. You can not see there was ever a run! Try it.


From contributor X:
Yes, I'm talking about automotive 2k waterbornes. The pricing is similar to that of Milesi or other top quality 2k SB clear coats. I've been looking into Dupont's waterborne selections, as they have 2k urethanes for plastic in dead flat to wet look for use on a sealed (base coated) surface. These cost $160 a gallon here in Canada (compared to Milesi at $150 a gallon) through my supplier for Dupont and SW automotive. I plan on trying this out on some fir entry doors at some point in time.

I'm still looking for other 2k waterbornes for wood but have yet to find anything other than chemical cure urethane epoxies (wb) for wood. Like I mentioned, in some cases the durability and chem resistance of a single component WB will not match that of a 2k like Milesi or other.



From contributor J:
You mention you spray USL and then topcoat that with the 9300. How many coats of each do you use?

I've been spraying ML Campbell's Polystar and recently had a couple problems with durability. In particular I had a d/w panel that the finish failed on. I'm respraying it now and am going to add a topcoat of Target CV (8000 I think), but I'm concerned with how much extra time it would add to spray another type of finish on an entire kitchen.

My current schedule is Polystar primer 4-5 coats, Polystar topcoat 3-4 coats, with approximately one hour drying time between, and light sanding between the primer and finish coats. The CV has a 2 hour min for re-coating, which is a bit of a setback. Ideally I'd like to improve the quality/durability of my finish without adding too many extra labor hours.



From contributor X:
I use USL gloss and make sure it has 12 ounces of pigment per gallon. I apply 3-5 color coats and 2 topcoats of the 9300 flat. I only wait 20-30 minutes or so between coats of USL (heated booth at 75F) and about 45 minutes for the 9300. I also only scuff lightly with p320-400 between coats as required. Typically this is for paint grade maple or birch and refinish jobs. I use the cheaper base coat because it's cheaper, and topcoat with a Cadillac.


From contributor D:
Contributor J, that seems like an awful lot of coats. Usually I just do 2 coats primer and 2 coats color with Polystar. Three coats primer if a lot of defects now and then, but you're talking 9-10 coats total. That's time and material consuming...


From contributor J:
Contributor X, thanks for the info. I do about an hour between coats because that's about how long it takes to spray through a full set of doors. My booth this time of year is about 65F but the finishes seem to dry okay. It's the CV dry time I was worried about. But 45 minutes wouldn't be as bad as 2 hours.

Contributor D, you're absolutely right. I wish I could cut down on the number of coats I'm spraying. But the Polystar primer doesn't seem to hide as well as I'd like. My doors are soft maple, so there's usually not too many defects, but it still takes quite a few coats to completely hide the grain. The topcoat also doesn't have good hiding, so I make sure the primer gets it white before I move to topcoat.

To be perfectly honest, I really don't care nearly as much about the cost/quantity of the material as much as the time in labor. An extra gallon of finish worked into the cost of a kitchen vs. an extra day or more of labor is a no-brainer.

I'm now wondering if I should look for a consultant to come in and spend some time looking at my setup and technique.



From contributor W:
I am an on-site finisher who works with painting contractors on architectural jobs. The main reason I switched to water based finishes was to eliminate the risk of flash fires when spraying nitro and CV's in a new house. I figured that the painting contractors were already spraying 100% water based paints (interior and exterior), so why should I be put at risk of causing a fire or explosion?! I had used WB's in my wood and concrete floor businesses with excellent results - so it just made sense to me to continue with what works and to avoid the liability. I would read the general contractor's paint specs and see WB paint for all of the wall treatments, but then the spec would read "nitro lacquer" for all of the brightwork! So I made the professional decision to buck the GC and do my own thing. The decision has paid off well for me.


From contributor C:
If something will give the same results or better, then it will be used. But it has to prove itself in all areas of concern by the finisher before it will be accepted. I have been around from the beginning of the waterbase craze, starting with Hydrokote. Yes, it has come a long way since then, but is nowhere as versatile as even the least nominal solvent base coatings. The reason? The chemistry! All are coalescent finishes. That alone makes them undesirable.

Here is a test I put all waterbase finishes through. Take a polyethylene lid from a coffee can or some other top and pour about 20 mils of your favorite waterbase into it. After it is dry enough to remove without losing its shape, take it out of the lid and leave it to cure thoroughly. Depending on the coating, this may take months or longer, so don't think you're going to see the results anytime soon. At the same time, take your favorite solvent base coating and do the same thing. These results will be quicker, needless to say.

As the weeks go by, what you will start to see in the water base coating is that the film contracts and misshapes unevenly due to the unequal drying of the film and release of water. Later you will see even a clear gloss water base start to turn milky, then toward the end of the cure, it will fracture into pieces like a dinner plate that someone hit with a hammer. Only no one has touched this film. As you see these (what are referred to as unsupported films) go through these stages, and see the solvent base film stay together, you will be skeptical of the long term performance of these products compared to solvent base products - even lowly nitro or solvent acrylic coatings.

If I test a new generation of coalescent finishes that perform like solvent base coatings in all aspects - especially longevity and appearance - I will become a user. But as long as the chemistry needs glycol ethers to wet the resin particles and water for suspension, I see no long-term viability for those products now available. My opinion? Yes, but based on sound coatings chemistry. Maybe for short term maintenance coatings it will be around forever, but I will never use the present coatings on something I want to last for 20 or 30 years or even longer.



From contributor D:
Who puts a 20 mil wb finish on? That's a test designed to produce a failing score every time. Maybe you should come up with more of a real world testing scenario.


From contributor X:
Contributor C, I have a few dry film samples such as these. The acrylic ones are all hard and brittle similar to a NC lacquer would be. The urethane ones and the polycarbonate one that I have are very flexible and don't crack, even after 2 years. These are more than 20 mils thick.

I have a thin polycarbonate film that peeled off some plastic I used to mask some windows and it's 3 coats thick at 4 mils wet (about 5 mils dry). It resembles clear plastic like a bag with about the same strength and flexibility (again, 2 years old now and still the same). You can crumple it into a ball and then unfold it all and do it again and again. Being a satin it's slightly opaque when you hold it up, but when you put it on a surface, it's clear, much like scotch tape.

I went through a lot of different testing and experimenting and am still developing new waterborne finishing techniques. I'm sure that these coatings are much more than a temporary coating for the kitchens and millwork I finish.

The other day I made a simple glaze that will work with most any WB system out there - just mixed some raw umber UTC with some water. I spray this on the panel where I want it with a detail gun, let it dry and sand off the excess with a maroon scotchbrite (works just like Amazing Glaze SB). WB finishing is different than SB, yes, but once you get used to it, the WB system is very versatile.



From contributor B:
I don't see where anyone has mentioned the equipment that is used to do the 3-4 or more primer coats, 2-3 color coats, or 2-3 top clear coats. I think that there are a lot of topnotch WB products available now that were not some years ago. I too started off with Hydrocote way back when. I do most of my finishing in-house with SB. I can, when forced to, use WB on site. I have some WB products I like, but have found that I can't spray with some of my equipment unless I thin them down, so it takes longer to dry, more spray passes to cover, more time and expense for total job. I have most any type of equipment available, but what I like to spray waterbase primers with is an airless... just like your house painters with their thick latex paints. Just get the right setup on tips, such as FFT tips or 311's or 411's, or even larger if needed. It's the spray technique that you can use to cut down on the number of passes (coats), therefore cutting down on some of the time that it has been taking for your cup guns or even a Kremlin. Yes, the airless can outspray a Kremlin if you are the sprayer to move out with it. Takes practice, but a good airless man will run circles around a Kremlin or cup gun guy.


From contributor J:
I do feel that everyone is entitled to have their opinions and use the products they want to use. However, I also feel that saying a new product has to exceed the old product in every way before you'll use it, is a very limiting view. There is a real world point of view that says sometimes the best is not as practical as something else.

Case in point, the overwhelming majority of walls in our homes are painted with latex paint. It's not as durable or good looking as oil based (in my opinion anyway), but it's much more practical, quicker to apply, and cost effective compared to oil based. People realized they just don't need the extra durability oil gives and even the trimwork is moving to latex.

If I'm painting kitchen cabinetry, I just don't have the same requirements for a coating that an entry door, or an automobile, or a nuclear submarine would. I don't need the most durable product that exists; I want something that will be appropriate for the work I'm doing. For my work I find that I can get something in WB that does what I need it to do.

I do think, like many others, that WB is the product of now, not just the future. And the more the industry uses it, the more it will be improved upon and refined. Most of the solvent based products out there that people are so attached to haven't been around much longer than WB anyway. Wasn't all that long ago that shellac or oil were pretty much your only options. My guess is by the time I'm ready to retire, solvent based will be pretty much nonexistent in all but the most specialized coatings, and the WB will be much different from what we're using today. Just my opinion based on very short experience spraying both solvent and water based coatings



From contributor C:
You don't need to pour a 20 mil coat, that's just me. 3 or 4 will be just fine. Any advances in the last 3 years are beyond me, so I apologize if there are any new ones I've not tested that have better properties. Keep your samples for a few more years and I think you will eventually see what I'm talking about. I am not interested in using them and they will never replace solvent base products in my shop.


From contributor D:
Never say never. Wait until the EPA comes in and tells you what to spray. Better be ready - that train's a comin'.


From contributor X:
The end is near for petroleum based products. You'll soon be looking for these on the black market, as inevitably all these coatings will be banned and even the waterbornes will be severely regulated. Seems air pollution is a bad thing these days.

Most finishing shops use pre-cat lacquer and CV and do the minimum number of coats to obtain a good finish. These cabinet shops are more concerned with price than they are with VOC emissions and worker health. I used to be one of these and could finish 200 parts a day with nitro and hardly any fancy equipment.

Contributor B, you should be using a 1.4-1.8mm tip size for a conventional or HVLP gun. You can go even bigger with some coatings (2.2-2.6mm). Most manufacturers will help you with viscosity and your gun setups.



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