Replies

1. 
   Ardito | Aug 09, 2004 09:45pm | #1

   Did you shake or stir your polyurethane?  More than likely the air bubbles were introduced to the polyurethane if the can was shaken.  I only stir my polyurethane finishes and pay extra attention to get ALL the goop from the bottom of the can mixed into everything else. 

   Dark Magneto

1. 
   OneofmanyBobs | Aug 10, 2004 04:57am | #2

   Also, do not wipe the brush on the side of the can.  Dip it straight and only a small amount.  Let it drain by itself.  Can also be too hot and the thinner is flashing too fast.  Thin it a little.  5 or 10%. 

2. 
   EdHarrow | Aug 10, 2004 06:06am | #3

   What you really need are my Great Uncle Dick's varnish brushes - they are so experienced at this point that all I need do is open the can and whisper the magic incantation, sit back and have a beer while they do all the work...  ;-)

   As was said, don't shake the can, and DON'T wipe the brush on the can.  In fact, don't use the varnish directly out of the can, just open the can and pour some varnish thru a clean, fine filter (pantie hose works great, too, DAMHIKT).  I like to add some Penetrol to the mix, maybe 10%.  I pour it into the filter first, then the varnish.  Don't forget to put the lid on the can, and I never return varnish to the can.  If you are taking a break, put some saran wrap over the top of the can from which you are varnishing (I use yogurt containers), and wrap the brush as well.  To slow things further, you can put them in the fridge.

   After sanding the door (you might consider scotch-brite pads), vacuum it every way for Sunday.  Then tack it, don't rub it.  Some folks like to then go over the door with a lint-free rag dipped in thinner. 

   Dip maybe 1/2 to 3/4" of the brush into the varnish, and let the excess drip off.  I've been known to sort of shake the brush to help the stuff off, but that's not really a great idea.  Flow the varnish on the door, don't work it with the brush.  I like to put the varnish on in one direction, and then tip it off along the direction I'm working, if that makes sense, towards the work I've already done, lifting the brush as I go.  If you can take the door off, that will help eliminat runs.  It only really counts when you get to the final coat, so all this is practice.

   And no, Uncle Dick's brushes are not for sale!

1. 
   Hoops70 | Aug 10, 2004 08:32pm | #5

   I appreciate the help.  I just wanted a little clarification.  Are you stating that I can fix the current problem by sanding the out with a scotchbrite pad?  If so, what type of grit would I use?  I was going to use a fine grit wet sanding paper (not sure what grit).  Would that be too fine?  I received 2 responses that both point to at least one of my problems, I was dipping out of the can and then removing excess on the side of the can.  I will definitely fix that problem.  As far as thinning, what should I use to thin?  Is Penetrol the best or could I use mineral spirits?  Is it possible the air bubbles are because the varnish is too thick?  Sorry for so many questions.  I put so much time into preparnig the surface, I just want to get it right on the last step.  One final question, how many coats would you suggest for a door that gets ~4 hours suna day?

   Thanks again

1. 
   Gretchen | Aug 10, 2004 09:04pm | #6

   Yes, you are getting air bubbles because the varnish is too thick. Thin with mineral spirits.Gretchen

2. 
   EdHarrow | Aug 11, 2004 12:58am | #7

   Ain't varnishing fun ;-)

   It's hard to know exactly what you have since we can't see it.

   Gretchen noted that your bubbles are being caused because the varnish is so thick.  I would clarify that slightly to say that the bubbles may be staying there because the varnish may be too think.

   Bubbles come from:

   Shaking the canScraping the brush on the side of the canOver enthusiastic application on the surfaceBrushing across things like moldings, corners, etcAnd probably some other things I don't remember (Sorry Uncle Dick... )

   Depending upon the state of your bubbledom you may well want to sand back to the begining... (well not actually want to, but you know what I mean).

   My suggestion re scotchbrite is that, IMOO, many people sand too much of the previous coat off.  Hopefully, all one needs to do is to just scuff up the surface a bit to give it some tooth so the next coat can have something to which to grab on.  If there's "stuff" in the previous coat, again it's a judgement call as to whether it will be a problem.  Most little bits of stuff you can deal with by a quick swipe over the surface with sandpaper or scrotchbrite pad.  Hopefully the next coat or two will cover it up.

   Also, re-reading your original post, I see where you are blowing it off.  That can actually work better than vacuuming...  You might check with your library to see if you can get a copy of "Brightwork", an treatise on varnishing by two sisters.  Everything you ever wanted, or didn't want, to know on the subject.  It's worth the effort for the pictures alone.

   How many coats - there's never enough, LOL.  I'd say four as a drop-dead minimum if you're in the northern (or extreme on the bottom side) side of things.  Seven would probably be better.  Just remember, you'll get better every time - practice makes perfect.

   That, now brings the subject of brush cleaning, on wish there are many different opinions.  I use water-rinsing brush cleaner, two soaks, dirty and clean (and no, I don't use the same brush cleaner that I've used for paint brushes), and then wash in hot, soapy water and hang out to dry.  Once dry I wrap them in newspaper.  Other folks leave their varnish brushes HANGING (emphasis that the brushes are not setting upon the bottom of the container, one never wants to do that to good brushes) until ready to use.

   Re thinner - again different schools of thought.  Most will suggest, I think, thinning the first coat.  Directions on the can should help here.  Penetrol, hmmm, well Flood doesn't call it a thinner, tho it sort-of has that affect.  What Penetrol does do is delay the drying, helping to maintain a "wet edge", which helps prevent overlap marks.

   If your door is a simple, plane surface, you might try applying with a roller, and then tip off with a brush.  The only time I tried that it was a disaster, but lots of people swear by that technique.

   Good luck!

3. 
   Alan | Aug 11, 2004 01:13am | #9

   RookieVol,

   Wet sand the current coat with some wet/dry paper, about a 400 grit, with a drop or two of soap in the water--or use wool lube if you have some--and see if that takes care of the bubbles.  It's likely that you'll need to do nothing more because, like all bubbles, they like to rise to the top.  If you still see bubbles, try wet sanding again before doing anything drastic.

   As others have said, bubbles are most likely to come from improper technique.  In addition to what the others have said, another place you can introduce bubbles is by working the varnish too much, especially if there are raised panels in the door.  Poking and jabbing your brush into the corners of a raised panel can cause bubbles, as can overworking any area with your brush.  Also beware going over the edges because that too can introduce bubbles.

   Again, as someone else said, flow on your varnish with long, even strokes.  Ideally you want to take as few strokes as possible and still get even coverage.  Long, even strokes, working with a wet edge, and not going back over things will eliminate most problems.  A little practice and a good badger/fitch brush will make you an expert.

   You can thin your varnish.  But thick varnish doesn't cause bubbles.  Bubbles are caused by the various things others have already covered.  As others have hinted, with good technique you can certainly put on full strength coats with no troubles whatever.  Thinning will make more work, and will necessitate more coats, which means there are more chances for things to go wrong.

   I confess I don't follow all the advice you've been given.  I don't let my brush drip off the excess.  I put my varnish in a scrupulously clean paint bucket, dip the end of the brush, and then remove the excess by gently tapping the bristles on the side of the bucket--not the edge, the side.  It's not created any problems doing it that way.

   Alan (going on too long again)

1. 
   Gretchen | Aug 11, 2004 04:09am | #10

   'way too many ideas here but I don't think the bubbles are because they are too thick.

   Gretchen

   Edited 8/11/2004 6:31 am ET by GRETCHEN

3. 
   GHR | Aug 10, 2004 07:53am | #4

   I used to believe in magic but ...

   I never sweep my floor so the air always has dust in it. My clothes are often dirty - more dust.

   I shake my varnish well.

   I pour some oil based poly varnish into a paper cup.

   I add some thinner.

   I swirl the cup.

   I apply with a paper towel. (I add some thinner if the towel starts to stick.)

   Pour the remainder into the can.

   I apply coats every once in a while depending on my filler jobs - a bit of lawn mowing or lumber stacking.

   Let it set for a day or so.

   Lite sanding to remove any nubs.

   Shake, pour, thin and apply another coat thinned a bit too much. Wipe off before it dries too hard.

   Let set for a couple days.

   ----

   I guess that all that has to happen is you have to apply a few gallons of varnish and then you get good.

1. 
   GHR | Aug 11, 2004 01:03am | #8

   Also if you varnish when the temperature is rising, the wood may outgas some.

4. 
   splintergroupie | Aug 11, 2004 06:09am | #11

   <<Blew the dust off outside, then wiped with tack cloth inside.>>

   This door is still hanging? In the sun? Sun will cause bubbles, even if the coat was put on earlier, and the sun hit it later. It has to do with expanding air rising in the pores, as someone mentioned.