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Forum topic by Bsmoot posted 06-13-2010 01:40 AM 2620 views 0 times favorited 16 replies Add to Favorites Watch
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Bsmoot

64 posts in 2404 days


06-13-2010 01:40 AM

whats the best way to put on polyurethane without bubbles i am new to it and i think i see bubles in it and can i sand it to take out the bubbles please help just built a night stand and stained it then put poly on to bring out the stain am going to put pics of it on later

-- Bryant north carolina


16 replies so far

View Scott Bryan's profile

Scott Bryan

27251 posts in 3284 days


#1 posted 06-13-2010 01:52 AM

Bsmot, one way to help apply poly without bubbles is to use a wipe on poly. Bubbles, from application of straight polyurethane, can come from a variety of sources- the action of the brushing technique and from the wood itself due to air being forced from the grain by the liquid poly (oak is particularily bad about this). A wipe on product gives the polyurethane film time to release the air bubbles before being trapped as the poly skims over.

Another alternative is to use a blow dryer to remove the trapped bubbles by gently blowing on the surface of the poly. But I prefer to use a wipe on poly. It takes more coats to build the finish since the poly is diluted with a suitable solvent, such as mineral spirits or naphtha. But it goes on much faster than brushing and dries quickly. So multiple coats can be applied within a relatively short period.

-- Challenges are what make life interesting; overcoming them is what makes life meaningful- Joshua Marine

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kosta

946 posts in 2817 days


#2 posted 06-13-2010 02:54 AM

I usually use a clear gloss poly and I just use a paper towel to wipe it on.

-- kosta Virginia Beach, VA http://www.kostasworkshop.blogspot.com/

View NBeener's profile

NBeener

4808 posts in 2637 days


#3 posted 06-13-2010 02:58 AM

I’ve also found that you’re much better off stirring it, than if you were to shake the can. Shaking the can seems to introduce bubbles into poly.

-- -- Neil

View Dark_Lightning's profile

Dark_Lightning

2633 posts in 2571 days


#4 posted 06-13-2010 03:06 AM

I’ve put Minwax (satin) water base poly on with foam brushes (doesn’t work so great), soft cotton swabs like handkerchiefs (works great) and brushes (lots of bubbles). But my best result is from spraying with a high pressure rig like I was painting with lacquer. Go figure.

-- Random Orbital Nailer

View Jim Crockett (USN Retired)'s profile

Jim Crockett (USN Retired)

852 posts in 3196 days


#5 posted 06-13-2010 08:42 AM

Another vote for wipe-on poly. And, if you already have some, you can make your own wipe-on by mixing it 50/50 with mineral spirits. Actually, I usually go 60/40 poly/ms – I’ve found that mixture works fine and it builds just a bit faster.

Jim

-- A veteran is someone who, at one point in his/her life, wrote a blank check made payable to "The United States of America," for an amount of "up to and including his/her life".

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Milo

869 posts in 2782 days


#6 posted 06-13-2010 02:01 PM

Hair dryer idea works great. Just use a low setting, no heat.

-- Beer, Beer, Thank God for Beer. It's my way of keeping my mind fresh and clear...

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stnich

116 posts in 2387 days


#7 posted 06-13-2010 03:56 PM

I use MinWax Polyurathane extensively. On a flat surface I almost always use a foam brush and a cheap china bristle throw away brush to get into those areas that a foam brush won’t reach. When I’m done with either I wrap them in plastic wrap put them in the freezer and use them again. I get many uses out of the bruses this way. Make sure that you stir throughly. Don’t shake it that will only introduce bubbles. Some bubbles might appear do to the action of the brushing stroke. Just go slowly and smoothly. The bubbles will usually disipate as the finish cures.The bubbles that may remain will be easily sanded out before the next coat. I use 320 grit siiicon carbide paper. It takes multiple coats to achieve a nice smooth finish. I also use MinWax’s spray polyurathane for areas that are not flat. I have good luck combining the two products on the same project.

View gerrym526's profile

gerrym526

269 posts in 3271 days


#8 posted 06-14-2010 06:52 PM

I have been brushing minwax Polycrylic (water based poly) on my projects for years with no bubbles. There’s no secret technique-just buy the best nylon bristle brush you can find (think $15-20 for a 2 1/2 inch brush), and use a raking light source to see where any bubbles occur-just brush them out before moving on to another part of the project.
Have used the same brush for over 10yrs-clean it with mild dish soap and water, rinse thoroughly, and dry as much as possible. Then wrap it in a heavy paper towel (Scott’s rags in a box) and put a rubber band around it to keep its shape.
While I don’t disagree with any of the guys who recommend wiping, if you practice a little with the brush on some scrap, you’ll get the hang of how to brush and eliminate bubbles as you go.
Gerry

-- Gerry

View TheDane's profile

TheDane

4997 posts in 3126 days


#9 posted 06-14-2010 07:59 PM

Here’s another vote for wipe-on poly. I used to use old t-shirts, socks, etc. but had to start buying bags of lint-free rags at the local big box when I ran out of underwear.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View ajosephg's profile

ajosephg

1878 posts in 3024 days


#10 posted 06-14-2010 08:57 PM

Wipings ok but it’s real messy compare to brushing in my opinion. I also use Minwax Polyurethane gloss with a quality brush. I believe the instructions say to use as is – do not stir. I’ve never had any problems with bubbles. Since I don’t use a lot I only buy it in quarts. When I’ve bought it by the gallon, I ended up throwing a lot away because I don’t use it fast enough and it get’s too thick, and gets a film on the unused portion.

I think gloss gives a more transparent, deep looking finish than satan or semi-gloss. I hand rub the final coats to break the gloss so the finished product doesn’t look like plastic.

-- Joe

View HighRockWoodworking's profile

HighRockWoodworking

182 posts in 2442 days


#11 posted 06-14-2010 10:24 PM

Wipe on poly is the way to go… Marc at The Wood Whisperer has a great video on this called A Simple Varnish Finish if you want more info.

Rather than buy wipe on poly, I just buy the regular stuff and dilute it with half mineral spirits.

-- Chris Adkins, http://highrockwoodworking.com/

View lanwater's profile

lanwater

3111 posts in 2397 days


#12 posted 06-16-2010 11:27 PM

I have experimented with both brush on and wipe on. It took me more coats with wipeon to build up your finish. Gel poly works pretty good too.

I personnaly prefer the brush. I plan to start learning spraying this summer.

-- Abbas, Castro Valley, CA

View wisno's profile

wisno

88 posts in 2474 days


#13 posted 06-17-2010 02:50 AM

Bubbles can occurs in the all kind of finishing process not only in the poly finish.
It caused by many reason such as : too thick application of coating, the pores and grains character in the wood, the stain or glaze underneath that is not totally dry, the air temperature that is too hot, etc.
To heal your problem you need to sand your finish and re coat until your bubbles is gone. You need to do it carefully and need a lot of time to getting it right. Apply your coat lightly many times instead of apply thick coat, it help to avoid the bubble problem

Bubble problem in the wood finishing

good luck

wisn

-- http://www.wisnofurniturefinishing.com/

View barryvabeach's profile

barryvabeach

159 posts in 2506 days


#14 posted 06-17-2010 02:57 AM

Bryant, if it is waterbased, I strongly suggest you try this http://www.homedepot.com/h_d1/N-5yc1vZ1xkx/R-100070177/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053 the Shur Line edger. I don’t work for the co, but it is the best product for applying waterbased. You need to pour some finish in an aluminum pie pan to load it, or just tilt the can against it to load the center, but the bristles are short enough that it leaves just the right amount of finish if you spread it around. Make sure you use a raking light so you can see what is covered. Stinch is on the money that you want to stir not shake the can.

View closetguy's profile

closetguy

744 posts in 3355 days


#15 posted 06-17-2010 04:06 AM

It’s real easy to lay down thick coats when using a brush. Like some have pointed out, when wood starts warming up, it gives off air which will create bubbles in the finish if the coat is too thick. The best way to get a perfect finish is to wipe on thin coats. This method also ensures it goes on even. Minwax wiping poly is good if you want straight poly. I prefer to wipe General Finishes Arm-R-Seal on with cut up t-shirts. With any wipe on finish, it takes longer to build the finish up, but the results are worth it.

-- I don't make mistakes, only design changes....www.dgmwoodworks.com

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