Flow Enhancers for Waterborne Lacquer

Finishers discuss the use of flow-modifying additives, alcohol thinners, or silicone fisheye reducers in waterbased formulas. March 29, 2008

Are there any additives that you can add to water based lacquer (MLC Polystar) to decrease the surface tension of the product and help it flow out better? This might help eliminate fisheye and some cratering.

Forum Responses
(Finishing Forum)
From contributor D:
That's just a common occurrence with Polystar. All they told me was to try sanding the primer with a rougher grit. Give them another year - they might work it out.

From contributor I:
They make both flow additives and a fisheye killer for the Polystar. The fisheye killer does contain silicone, so if you use it, the equipment should be considered permanently contaminated.

From contributor T:
AquaStar WB Flow Enhancer.

Some additional helps:

1. Don't sand finer than 150.
2. Wipe the surface down with alcohol just before spraying.
3. Never thin with water - it will raise the surface tension of your finish. Use alcohol if you need to thin.

I'm not one who believes silicone additives permanently contaminate equipment. Fish eye is caused by local spots of very low surface tension material on the surface of your project. It is usually, but not always, silicone. These spots have a different surface energy or critical surface tension than the general field of your project and your finish will flow out differently (thinner) over these spots - causing fish eye. When silicone is added to your finish, you are simply reducing the surface tension of your finish; bringing it more in line with the contaminated spots. If there is no contamination, the additive will reduce the surface tension well below the critical surface tension of your wood - which also gives you better flow out. In any case adding a flow out enhancer to your finish does not cause local spots of contamination in the current or any subsequent loads of finish.

From the original questioner:
Thanks for the responses. Would adding alcohol increase the drying speed and therefore the finish would not be as smooth? Polystar lays down pretty good with a little water added to it on the last coat.

From contributor C:
Alcohol does speed drying time (versus water) but also decreases surface tension and helps to prevent skinning and clogging... On the whole I think that a little alcohol is a positive influence on getting a smooth coat off the gun. I often use mostly water (distilled or heavily filtered water is superior to most tap or well waters) with small amounts of alcohol (5 to 10 percent of thinner volume) for thinning. I believe that atomization is also enhanced by this small alcohol content and it seems helpful to me on a wide range of water based finish projects.

I know that some guys use Photo Flo or dish detergents but I have not needed them yet. They are intended to decrease surface tension without speeding drying time and should be effective too... I just find that better flow out reduces the need for slower dry times and there are many advantages to swift drying that I find desirable. I understand that propylene glycol is an extreme retardant that must be added by the drop... Usually it is used for glazes that require long open times for manipulation. I could see it being used for spray work too but given that the balance between runs and poor flow out is a delicate one, I personally find slight alcohol additions and thin, well atomized coats to be the most useful strategies.

From contributor W:
Alcohol will speed up the dry time of the WB finish in question, but the real question that needs to be asked is, "Why should a modern WB require flow additives and fisheye killers to work well and look good?" I have used the Campbell Polystar product and fought with fisheyes on a regular basis. When I switched to Target and GF and Becker, I did not have to add any sort of flow or leveling agent to their finishes to make them work. What this has led me to believe is that the Polystar product is a poorly engineered, outdated WB formula that requires the customer to play the role of the chemist in order to make the product work for him/her. Conversely, I have used both clear and tinted versions of Target WB's, General WB's and other brands that work very well right out of the container without having to fight with multi-coat application.

Granted, I have come across contamination problems with these products that resulted in fisheyes, but none that resulted in the need for me to add or play chemist with external flow/leveling aids. My advice to you is to find a new WB that will work well in recoat applications without the need to add a variety of secondary products to compensate for poor chemistry.

From contributor D:
The Polystar is a mystery. It is a great product. I use the primer for oil paints as well. We do the typical wood 150, 1st primer 220, 2nd primer 320, 1st topcoat 400, 2nd topcoat. No additives. I've experienced the dimpling once in a bad way and one other minor time. The MLC techs tell everybody use coarser paper, but you can see scratches at 220. I am especially fussy about cleaning my gun when I'm using Polystar. I also watch the humidity levels and never spray below 65 degrees.

From the original questioner:
I use the Polystar because there is a paint store that can match an exact color. The other companies that were mentioned are not located in the Seattle area.

Contributor C, I stopped cleaning the guns with any soap thinking that the additives used might effect the coating and instead used alcohol. What brands are good to use?

From contributor W:
Understood. Have you tried the MLC Aqualante WB product? I've used it on a few jobs and find it comparable to other modern WB's. The downside is that it's loaded with ethylene glycols = HAP's and other poor air quality effects. Not what a modern WB should be formulated with.

FYI... Call Target Coatings and they can get you set up with quick UPS shipments to your location. General Finishes can do the same.

From the original questioner:
Yes, I have used Aqualante with good results. Sprayed a colored primer and used 2 coats of Aqualante on top with no problems to speak of. It would be nice not to have to use a colored primer, but I prime anyway. One more item I should mention is that using Sealcoat does not seem to help, so there must be something wrong with Polystar or Sealcoat does not work with Polystar very well.

From contributor S:
Pull an Agualente p.i. sheet. I was under the impression this is a certified green guard coating with a VOC content of only 100g/l. How much lower in VOCs are the Target or General coatings?

From contributor I:

I have to side with contributor S on the Aqualente. I know it is being used in this state for a large amount of leed jobs. In my opinion it is better than any Target product I have tried.

From contributor T:
A little alcohol may shorten the drying time some, but as contributor C said, you're going to get better atomization and better flow out so a shorter drying time is not a problem. I haven't tried a mix of water and alcohol, but if contributor C says it is so, you can usually take it to the bank.

From contributor R:
Nobody has mentioned Target's flow enhancer - SA5 I think. I haven't done any scientific tests, but it does seem to work.

From contributor M:
I've been following this thread with interest. Alcohol = standard denatured alcohol or ? Would the addition of the alcohol help the new coat of finish bite into the previous, helping to avoid runs/sags on vertical surfaces?

From contributor A:
Are you guys advocating the use of alcohol as reducer/retarder in waterborne finishes? I would be amazed if it has no negative impacts on the final product.

From contributor I:
I do know that VanTechnologies uses Acetone and IPA in the wb's that I have used from them and that they recommend those two items for cleaning lines and guns. It would seem, then, that IPA for their products would be compatible. That said, you still have to determine how much of anything you can add before you change the characteristics or performance of the coating.

In my opinion the rep would be better suited to answer your question than any of us. That said, I have been told by an ML rep that the flow enhancers and fisheye killers are an option as I stated above.

From contributor T:
I recommended alcohol (I use ethanol) as a thinner, reducer, or diluent if needed for WB's, not as a retarder or flow out enhancer. Why?

Surface tension of:
water = 73 dynes/cm
n-propanol = 24 dynes/cm
acetone = 23 dynes/cm
silicone oil = 19 Dynes /cm

Thinning with water raises the finish's surface tension, which increases the probability of flow out problems. Thinning with alcohol (or acetone) reduces a finish's surface tension, which reduces the probability of flow out problems, but it will not get it down to the level of silicone. How much alcohol? I stay below 5%, but that's just my preference.

Alcohol and water are totally miscible. In fact they form a hydrogen bond (they like each other), which is why an alcohol flush is often recommended after cleaning WB equipment with water.

Minor flow out problems can be handled with a flow out enhancer which is probably a surfactant or soap-like material. (It follows that cleaning with soapy water does no harm - ammonia water works well.) Major flow out problems like silicone contamination will require the addition of a fisheye killer which is most likely silicone.

I got the tip to use alcohol rather than water to thin WB's from a rep a long time ago and much has changed in the world of WB finishes. But it still works for me. I would add that the chemistry of WB's is very complex and differs from manufacturer to manufacturer. In my opinion, you risk less by staying with one manufacturer's products and additives.

From contributor A:
Contributor T, do you have surface tension of prop glycol? MLC Flow Enhancer is glycol/water. Obviously, acetone, ammonia, denatured alcohol all can be used to cleanup waterborne products. However it still sounds pretty sketchy to me to add them to the product. Regardless of the chemistry contributor T mentioned, which is those products by themselves not in a complex solution of chemicals.

From contributor C:
I have used both isopropyl alcohol and denatured alcohol (from the paint store... various brands). Both seem to work fine. I am sure that professional paint chemists would have palpitations if they were forced to witness the daily activities of practical and experimental paint applicators like myself! Nonetheless, after many years of altering paints in many ways and communicating with many others who do likewise, you begin to lose the fear of the unknown (well, maybe it's just not that unknown anymore). I have used alcohol with many brands and types of WB paints and I know others who have done likewise with no discernible ill effects or coating failures.

Fear not, step forth boldly, and seize your destiny! Once you begin to do your own tinting and to tune your coatings for custom conditions or working characteristics, you begin to seize mastery of your medium. Soon thereafter you'll be a real finisher (not just a coatings applicator).

From contributor T:
Well said, contributor C.

I have glycol listed at 64 dynes/cm but I have no clue which glycol that is. PG/water sounds more like a retarder (butyl cellosolve is PG) than a flow enhancer, but maybe that's their approach - slow it down so it has time to level? The ammonia comment was in response to a question from the questioner.