Suggestions please: Alternate equivalents to Varathane "Colors In Plastic" (polyurethane) paint?

[Ken Moiarty]

I've been trying to do some sprucing up some assorted fixtures, moldings, and other miscellaneous household surfaces by brushing on white Varathane 'Colours In Plastic' (oil based polyurethane) paint. However, I'm finally throwing in the towel as far as using a brush with this stuff is concerned: Can't seem to avoid the creation of little pin-head sized bubbles everywhere. Most of these bubbles eventually pop on their own, but always too late in the setting process not to leave tiny pimple-like craters scattered everywhere, simply making for an unacceptable finish. I'm going to have to switch to applying Varathane paint by spray from here on. (I've discovered there's no problem with bubbles when applying the Varathane by spray.) But spray painting means having to move or remove whatever I want to paint with this stuff into an area suitable for spray painting and this just isn't practical for every surface I would like to touch up. Therefore, I'm looking for suggestions as to other products and/or other types of paint I might turn to that are like Varathane insofar as they produce a smooth, hard and durable enamel-like coating, but without the problem of countless micro-bubbles forming when being applied by brush.

TIA,

Ken

[m Ransley]

Bubbles are likely paint "fisheyeing" due to oil on the surface, did you clean what you are painting with denatured alcohol. There are alot of paints just as good

[Stephen Hull]

[snip]

Ken, Presuming the prepared surface has no contamination of any kind as you probably know grease, oil etc can create pinholes or craters. The pinholing which usually leads to tiny craters can be caused in many different ways, the most common is when paint material is applied too quickly or too thick, even excessive brushing can cause air to become trapped, this is more apparent when using polyurethane finishes.

It is possible that solvents may have become trapped in the substrate as the surface starts to skin dry, blocking solvent release forcing tiny air bubbles to pop into craters.

Scraping a charged brush on the edge of a paint tin instead of using an alternative paint tin will in some cases also produce air bubbles.

Air bubbles can be introduced in a paint material by over agitation during the initial stirring just prior to use. Air bubbles can sometimes be avoided by not over brushing and should be eliminated completely by adding a little raw linseed oil to ease off the faster drying properties associated with polyurathane finishing.

Steve.

[Goedjn]

Are you using something to either thin the paint or accelerate the drying? Are you trying to apply the paint it too thick a coat at once?

>

[Ken Moiarty]

"Goedjn" wrote [...]

No, no, and no. I have tried thinning the paint with mineral spirits. No benefit. And I have tried applying the paint thicker... this among numerous other ad hoc variations in 'random trial-and-error style' to see what, if anything, might work different or better (all to no avail, needless to say). Since posting this message I've poured over the internet reading about other people's experiences in brushing Varathane paint, and I'm now pretty much now convinced that the "tiny bubbles" problem when applying Varathane with a brush is unavoidable. I've developed the hunch that other people who seem to not experience this problem are maybe just not as fussy as I am with their work, and/or their lighting is such that these tiny blemishes are not so plainly visible and/or bothersome to them. (So as to see what I'm doing, in addition to normal overhead lighting I illuminate my painting surface with two 500 watt flood lamps, positioned at oblique angles to the major plane being painted...)

Ken

[Ken Moiarty]

"Stephen Hull" wrote

Hmmm... Raw linseed oil to delay drying, eh... I'll be giving this a try. I didn't know I could delay the drying time of Varathane, being that, ostensibly, unlike ordinary oil-based paints polyurethane solidifies not by solvent evaporation but by the chemical reaction of isocyanate reacting with the moisture in the air (which, as an interesting aside, is known to release CO2). Yet, there's obviously already some oil in this "oil-based" polyurethane product and this may, for all I know, perform discrete functions beyond the obvious. So who knows? It seems to me that this Varathane sets up so quickly, losing its ability to flow freely so soon, that the holes left by the bubbles don't have a chance to fill themselves back in. So maybe this will be the key. Thanks.

Ken

[Stephen Hull]

[snip]

Most people would automatically add turpentine or white spirit into paint in an attempt to retard the drying process when experiencing drying problems but these are also classed as driers and although they'll ease application it doesn't always decrease drying times.

There's a product called Owatrol that will also retard the drying process. Unfortunately Polyurethane is proven to set-up too quickly and sometimes needs a hand to slow it down.

An alternative method would be to use a recognised slower synthetic thinner perhaps 10% and if possible paint on a cooler day.

Steve.

[Ken Moiarty]

Woke up and couldn't fall back to sleep this morning so I decided to get up early and try painting again. I was impatient to try the "linseed oil" idea. But I don't have any linseed oil in the house and nothing's open here at 3 AM. So on a whim I used some food-grade MTC (medium-chain-triglyceride) oil I happened to have lying around (from my days if experimenting with fad body-building food supplements). MTC oil is a very light oil. But one advantage the MTC oil happens to offer as paint additive is that it is completely colourless. OTOH linseed oil being yellow, whilst my paint being white... well you can see where I'm going. Anyway, I just finished putting up a coat of Varathane, after thinning it with this MTC oil. And man, what a difference! Although a little on the runny side for my liking, the problem with the bubbles has now been completely resolved! By delaying the Varathane setup, and thereby increasing my time to work with it, I am now able to painstakingly tease out all the bubbles with my brush before leaving the project to dry. (Also, as a bonus, brush marks now less prominent. I'll see later if they don't have enough time to disappear completely on their own before the paint does finally begin to set.)

Thanks again, Ken

[Stephen Hull]

In the coach painting industry it has usually been the norm to speed up the drying process particularly on finishing coats as this type of paint can stay workable for hours, mainly because it contains more oil than pigment and less drying agents are added.

Modern paints unfortunately tend to dry from the opposite end of the scale, too quick, probably for faster reapplication and quicker turn around.

I've heard paraffin can be used to slow down the drying process but wouldn't recommend it, it's not pure enough to use in paint. However your MTC oil method seems quite a plausible solution.

The colour of Linseed oil is on the yellow side but it would hardly make any difference when added to white especially in such small quantities.

Anyway I'm glad you've managed to get it sorted.

Steve.

[Ken Moiarty]

Latest Entry: Just got home from work to find my paint job still just as wet as when I applied it, which was well over eight hours ago. Obviously I used too much oil in my 'test sample'. Fortunately this was only a test paint job, and not the real thing. I'll have to attempt this again, only with much less oil. The upshot of course is that I have not yet in fact solved my "Varathane bubbles" problem afterall; as I had so enthusiastically -but prematurely- concluded in my previous post. But I am still quite certain that you have put me on the right track towards getting there in pursuing this approach.

Ken

[jtnospam]

You may want to just use a plain old oil-based enamel, the polyurethane is probably "overengineered" for your use anyway. The commercial "boiled linseed oil" has chemical drying agents in it that will allow it to set up in a reasonable period of time, not so with raw linseed or apparently your MTC oil. Best wishes on your projects.-Jitney

[Norminn]

clipped

Have you shaken the can prior to appl? Using good quality bristle brush? Brushing too much? Clean surface?

[Norminn]

Are you serious? :o) You can try butter - that way you can just wipe it off when you get tired of it, because it will not be dry :o)

Stir the stuff gently, do not shake. Use good quality natural bristle brush. Thin per the label instructions. Do not use linseed oil. You may be putting it on too thickly, or brushing out too much.

[Ken Moiarty]

Not a good idea... (Perhaps I should clarify: my description of the problem would be different if I hadn't already been successful in preventing bubbles from forming in the paint prior to its application.)

Two $30+ Purdy's. One synthetic, the other natural bristle. The best they have in my local HD store. HD is not the ideal place to shop for quality, I realize, but could a better brush than these really make a difference in a problem of this description?

Initially.. clean but not obsessively so. But as I've kept doubling and re-doubling my efforts to assiduously control for 'this variable and that variable', so as to get at least a handle on the problem... well let's just say I don't know how much cleaner it could get beyond what I have since been getting it.

Ken

[Ken Moiarty]

Norminn,

Just curious... Have you yourself done a paint project applying Varathane paint (i.e. Colors in Plastic) with a brush? And if so, had you not experienced this problem with "tiny bubbles" forming upon application, such as what I have described (and which I have become frustrated enough by to try everything 'including the kitchen sink' to overcome)?

Ken

[Ken Moiarty]

Thanks for your reply. I hadn't realized (until now) that my news reader has been set by default to limit messages to 300, and your message didn't get downloaded. Since changing that setting I'm seeing messages I never saw before, including yours.

Oil on the surface... clean with alcohol, hmm... I'll give this a try next time I have a fresh surface that I want to apply Varathane (or other polyurethane) paint to. Thanks.

Ken

[Ken Moiarty]

I didn't think so.

Ken

[Grolsch]

Raw Linseed Oil! I don't think I'd add a non-drying oil because of the effect on final cure and film properties. Adding a little boiled linseed oil would work though. A trick we used to use when painting gloss enamels in cold weather was to add a touch of boiled oil AND a touch of Japan Driers. This improved flow-out while still able to cure a reasonable rate.

[Grolsch]

I have had similar experiences with different "urethanes". Varathane is a Urethane modified alkyd. Some causes of "pinholing" are:

Poreous surface/substrate - material gets into the poreous substrate, the surface of the applied paint "surface cures" (skins), then the trapped solvents break through this "skin" after the material is past optimal flow point. Adding more and more volatile solvents may compound the problem. DuPont makes a product for the automotive finishing industry called Fish-Eye Eliminator (flow modifier), It works quite well. Also most makers of Urethane have "flow modifier" solvents.

Applying too thickly. Again, trapped solvents must breakthrough the surface skin.

Excessive volume of hot or warm air will increase surface drying and compound the problem.

Try thinning as per label, don't use heat or fans if possible or use them indirectly (don't blow heated air across the surface). Also try putting on a very thin coat (20% thinned) to fill surface porosity (?).

Also try foam brush or mohair applicating "pads". I have had good success with them for small jobs.

Larger items are probably best sprayed.

FYI, I am a Journeyman Painter (28years), NACE Certified Coating Inspector. I know of what I speak!

[Stephen Hull]

Indeed,

However during certain coachpainting processes Raw linseed oil was added because it is a (less cooked) slow drying oil that did slow down the faster drying oil paints and varnishes, which already contained a high proportion of driers, thus gave an overall better drying balance.

It was not uncommon with certain pigments when applying paint by brush to paint a complete panel, then go for lunch and return an hour later and the panel could still be layed off. This was only necessary on troublesome pigments where the naturally slow flowing out properties had been undermined by faster acting driers which the painter had no real control over being already pre-manufactured paint etc.

Steve.