Boat Forum / Cruising / January 2005

snip..

Just a thought...do you stir the can of varnish slowly and carefully before
applying?   (not like paint can shaking)

Varnishing can often be more "art" than "science".  I don't consider myself
a "pro" by any means, but have spent enough time around the pros to pick up
some of their tricks.  Sounds like you're using all the main ingredients to
a successful varnish job:

* using a good brush, "China Bristle" or better, although foam brushes have
worked for me,
* never shake the can, stir -and- strain the varnish to a separate
container,
* Schooner Varnish is the preferred varnish of the pros I know,

A couple things you didn't mention though, and I'd add:

* surface prep:  make sure you thoroughly clean and tack rag the surface
before each coat (contaniments can cause what appear like bubbles).
* air temp / humidity:  calm, cool and dry mornings are often the best time
to work, gives the varnish more time to settle before drying.
* lots of coats:  8 coats as a minimum, most pros I know go with 12 or more.
* brushing technique:  sounds like you may be moving the brush too quickly,
thus generating bubbles.  Also brush in one direction, not back and forth.
Try to "flow" the varnish on rather than "brush" it on.

Of course, there are days when the varnish just doesn't want to cooperate.
The "cheat" I've seen the pro's use is using very heavy coats, and "flowing"
the varnish on, then if it still won't level properly, they'll wet sand and
polish as a final touch.

Some folks love doing brightwork, others (like myself) see it as a necessary
evil.  Trust me, you aren't the first to be frustrated with a varnish job
that just doesn't want to work.

Good luck!

Paul

The bubbles that form during curing are usually caused from varnishing
during rising temperature. .  As cold wood warms the air in the pores
expands.  I try to lay the first couple of coats late in the afternoon while
the wood is warm.  As it cools the air contracts and sucks a bit more
varnish into the pores.

In my not inconsiderable experience with wood finishes I have to note
that varnish is one pain in the butt finish to apply when compared to
many other finishes. Unfortunately, with bright work, the options I have
open to me for other applications aren't viable.

First, gloss varnish doesn't need to be mixed. Semi and satin does.
Never shake the can, stir gently to avoid suspending air bubbles in the
finish before you even start applying it.

Thin your first coat or two by 50% and apply it with a rag.

If you use a brush be sure it is a natural hair brush, badger, and do
not tap off the excess into the can. Gently move the brush across the
mouth of the can to get excess finish off.

Thin the varnish to around 15% for follow up coats. The less viscous
coat allows air bubbles to escape faster.

Start you brush stroke with the brush tip and held almost vertically to
the surface being coated. Draw the brush slowly across the surface
lowering the angle of the brush as the varnish flows out.

Tip off the coat. That is, once you have the stroke finished very gently
and with just the tip of the brush touching the finish at 90 degrees
move it across the finish to knock out any bubbles you do get.

DO NOT over work the finish. It is almost impossible to not get some air
bubbles in the finish. As you have found, overworking the finish just
makes matters worse. That is what they make sandpaper for.

DO NOT try to sand off drips and sags. Use a sharp chisel or razor to
shave them off.

If at all possible DO NOT varnish in full sun. This causes the finish to
skin over much too fast to allow any air trapped in the grain of the
wood or laid down by the brush to escape.

DO NOT apply thick coats. Thin coats are best! Thick coats also slow the
rising air bubbles to the point where they become trapped in the curing
varnish.

DO Not bury bubbles and dust bumps under another coat. Sand them out
before the next coat. Waiting, of course till the coat is cured at least
eight hours. If I am using an oil based varnish steel wool is my
preferred medium for doing that job. If you are using water based
varnish steel wool is ok for the last coat but you have to use sandpaper
for the in between coats.

Decant the varnish to another container for application. Do not put your
brush into your main supply or dump anything left in the second
container back into your main supply. Doing either will contaminate your
main supply with anything your brush picks up. Pour slowly to avoid
introducing bubbles into the varnish.

Thin coats means you have to apply more of them which takes more time
but they avoid a lot of the problems inherent in applying varnish.

My preferred method of applying varnish is to head down to Lowe's or
Home Depot and pick up a large box of Scott's "Rags in a Box" wipe on
the above mentioned fifty percent thinned coats then thin the varnish
somewhere between fifteen to twenty percent, the figure isn't critical,
and wipe on the rest of the coats.

While the above method, what with thin coats and drying time between
coats, takes more time to get a good build then brushing on a few heavy
coats it avoids most of the problems brushing on heavy coats introduces,
air bubbles, drips and sags, dust collection, and can, if one is looking
for a really good finish, actually reduce the time it takes to get one
since you aren't trying to fix those problems.

The use of thin coats makes no difference in the durability of the final
finish.

I may have forgotten a few things there but it's somewhere to start.

Hope it helps
Mike G.

After 8 coats the bubbles would not be coming out of the wood.
So are your sure that they are not small bits of contamination? I've had people
tell me that the bubbles they see while applying varnish don't seem to fully
pop and go away. And after looking closely at them I've found them to not be
dried bubbles but particles of contamination or dust.
Are you filtering the varnish? Tacking off well?
Applying it outside? Or in a dust free room/area?

If they truly are bubbles perhaps you should add a bit more thinner (if your
adding any now) to give the bubbles less viscosity to fight and more time to
pop.

                                  Capt. Bill

I'm sure you've seen by now that any question about varnish on this
group will bring out enough responses from the "varnish is evil" crowd
to make you want to hang up your brush. ;-)

Of course if you've read Rebecca Wittman, you know to pour from the can
through a filter into a container and then thin and brush from that.
Keep everything clean. Tack rag and wipe with mineral spirits. Yadda,
yadda. If you've done all that you may still be experiencing any one of
several problems.

First, as has been mentioned, be sure to start with one or two very thin
coats to seal the wood.

Second, make sure your varnish is properly thinned. This depends a lot
on temperature and humidity. Knowing what's best comes with practice. I
usually try to get a consistency between whole milk and half & half. See
how it drools off your stir stick. Err on the side of too thin.

Lastly (and I think this may be where your problem is), there's a
technique to brushing. Don't overload or underload your brush. Brush
with the grain of the wood and try to brush away from your "wet edge".
Start brushing for coverage and then go back several times, each time
with less pressure, finishing with strokes so light that you're barely
touching the surface. Once an area is done, don't touch it again until
it's dry. You can get good results with foam brushes, but I think
bristle brushes produce fewer bubbles.

After saying all that, you should know that it will never be perfect and
there's no such thing as a final coat. If all else fails, you can always
invoke the "4 foot rule". Think of varnish as a "zen" exercise and don't
let anyone ruin it for you.

Cindy