I posted this message in the wrong forum, so I will repost it here:
What is the best way to apply a water-based acrylic polyurethane over broad, flat surfaces? I have tried using an ultra-low nap roller and laying it off with a paint pad, with a stain pad and with cloth. I have also tried raging it on. In both cases, I end up either with bubbles or significant streaks. Once sanded down, the bubbles leave little craters. If I sand the streaks or bubbles all the way down, then I’m back where I started.
What is the best way for me to apply this product without having streaks or bubbles left after it dries?
Replies
There are brush on acyrlics from the consumer grade manufacturers. These call for a good synthetic varnish brush. The application looks pretty much like oil-based varnish although you still should work rapidly, but without vigorous brushing that could create bubbles.
The professional grade products--Target and Fuhr, are designed for spraying, but can be brushed if they are treated as if they were shellac, with a watercolor wash brush (low reservoir, very fine bristle, especially Taklon gold) and very thin applications were you can't expect to go back over any area a second time.
Rollers, foam brushes, pads all work well for some, but I have never been happy with them and haven't worked with them enough to discover tricks of the trade with those.
Thanks for the suggestion.I have been using Old Masters brand, which was recommended to me. Have you had any experience with it?
No experience with Old Master brand. I have used Target, primarily.
Steve,
I used to spray only Fuhr's pre-catalyzed lacquer, but have had excellent results using Minwax's Polycrylic (it's advertized as a varathane-like top-coat). I am using a Lemmer HVLP compressor-driven gun, with my compressor set to 55psi. The main reason why I even tried anything other than Fuhr's products was the lag-time for ordering their product. Although my local supplier is only 50 miles away, the local Home Depot is 2 miles from my home... and the results I'm achieving are solid.
Marty
(Sawdust Eater)
If you are getting bubbles or streaks, look to your technique. Bubbles result from too agressive brushing or wiping when applying. Finishes should be flowed on with minimal back and forth brushing. They should also be "tipped off" by using a brush with little finish and lightly drawing the stroke the full length of the surface. This will help the flow out of the finish and break up bubbles. With large surfaces you need to work quickly as waterborne finishes dry quickly.
If you are using a non-gloss finish, and the streaking is sort of a cloudy or foggy nature, you may not be stirring a the flatteners completely into the finish. Stir 100 strokes in one direction, and then 100 strokes in the other. Restir occasionally during application.
Could I use a paint pad to apply the finish (the kind used to apply urethane finishes for floors)? What would happen if I didn't tip off or lay off?
I'm not Howard, but in my opinion, the tipping off is THE most important part of varnish application. It is what levels the varnish, eliminates brush marks and carries off any bubbles. Paying attention while tipping off also reveals other problems such as a drip or a holiday while they can be corrected. You can get the varnish on the wood in a variety of ways, and the only real rule is not to slap it on so vigorously as to generate bubbles, or so messily as to create drips and runs, or so carelessly that places are skipped. But the tipping off is what equalizes those other methods and generates a good result. Again the tool is a good chisel tipped brush, synthetic for waterborne finishes, natural for oil based.
And is it not true that you should not "drain" the brush against the side of the can? Can't think of the right term.Gretchen
The injunction is not to drag the brush against the rim of the container since this can create bubbles. I suppose it makes sense, but adding the right amount of thinner is the best defence against bubbles for an oil based finish. For waterborne you can only add a small amount of distilled water. If you still have bubbles, change brands, since that is one of the properties under the control of the manufacturer and his choice of additives.
One more thing, you should always pore the finish from its original container and brush from that, not the entire can. Otherwise you can contaminate the can with dust etc. picked up by the brush. And when you have finished don't pore any remaining back into the can.
Edited 3/10/2006 9:19 pm ET by SteveSchoene
Actually, the recommended way with any finish is to put some in a container and not take it from the can. This way, anything on the brush won't contaminate the rest of the material. Don't scrape the brush on the side, just tap it so the brush has the right amount on it.
"I cut this piece four times and it's still too short."
Pads are fine for applying finishes to floors, particularly if using a waterborne finish. But, I don't like it for oil based finishes where you want top appearence.
The way to a smooth finish is careful application paying attention to "tipping off" as Steve indicates. Second, thinning of today's VOC compliant finishes is very important.
Finally, brushing on a finish is something that is not learned in a minute. It requires practise and experience. The more you do it, the better you become.Howie.........
I wanted to add a little from my experience. The bubbles can be caused by over brushing or in the way you get the poly ready. When you shake paint or poly you create air bubbles. You should only stir finishes. I used to shake the can because I thought that would mix the contents the best. That only creates bubbles. When you buy most finished you can get the store to shake the can. This finish should sit 24 hours before use. Then you can stir and stir. The next problem is with streaks. The brush has the most to do with the streaking problem. When you apply the finish only apply it once and let it alone. Do not retouch unless there is an obvious defect like a finger print. You should apply the first coat of water based poly let the finish dry and then smooth the surface with synthetic steel wool. Real steel wool leaves small slivers of steel and they will "rust". The surface preparation is most important. Use 100, 150, 220 or higher sand paper progressively. Skipping a grit will cause the wood to be microscopically fuzzy. Each grit of sand paper is engineered to be smoothed by the next higher grit. If you sand with 100 and then finish with 220 you will take longer and get poor results. That causes your finish to look fuzzy as well. The poly needs about 3-4 coats to look its best. That would be 3-4 thin coats. Every coat, especially the first coat will not be perfect. Most people want to hurry through with the finish. The finish is what most people will see and judge your work by. You may have taken days to build a small box then rush through the finish and the outcome is poor. It is hard in our modern world to be patient but patience gives the best results. The more you do finishing the better you are at it. Each time you should learn something about methods, that includes good and bad methods. When you finish a project you should critique your work and make a note of what worked and more importantly what did not work.
I have had excellent results with "Genral WB Poly" from Woodcraft - IF it is applied with a synthetic brush. Any other applicater leads to problems.
Jerry
I have used water based poly many times.
I use a throw-away foam brush. You can also use a synthetic brush. With the methods you describe, you are kind of 'pushing' it on, instead of laying it on.
You may be getting bubbles from shaking the can, as someone else has mentioned. Rollers will cause bubbles. Foam brushes can cause bubbles if you are not careful. I suspect you might be putting too much pressure on the brush to spread on the finish. Let the finish flow on with a wet brush. Water-based poly is tricky that way, it is quite different from oil based poly.
First let the brush soak up finish. Dab it against the side of your working container softly to get rid of excess. Do not drag the brush over the edge, that will introduce bubbles. Lay down the poly quickly but softly. If you have to press hard, you do not have enough finish on the brush, and you will introduce bubbles. You will have to dip often on the first coat. Do not re-work the first coat any more than absolutely necessary. It will not look very good in any case, you need several coats. Water-based poly cannot be re-worked well (feathering), and starts drying very quickly.
The next coats will flow on easier, and you can work the next coats a little easier. Sand between coats as necessary, and wipe down well with a clean cloth.
You also might practice your technique on waste material untill you get the hang of it. Brush from inside the edge, out over the edges, in the direction of the grain. Do not drag the brush from outside the egde inward, that will introduce bubbles and cause drips.
Good luck,
Ray Fitzgerald
My way is to stir SLOW when mixing and use a paint pad with most of the finish "wiped" out so there are no drips from the pad. It drys fast so you can over push the finish and end up with streaks or thin areas.
The best way I have discovered is with a HVLP spray system. It takes a little bit of practise on casework, corners, inside cabinet etc. but the finish is so superior it is worth the time and money.
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