Frank Wentzel
10-22-2002, 04:14 PM
Author Topic: Spray Varnish?
Joe Murli
posted 04-23-2000 12:34 PM
I have a LOT of varnish to put on. It's a 39' Ketch with a mahogany
cabin house. Has anyone had any experience with spraying varnish?
Can I use an airless sprayer? HVLP? How about rolling?
Help, I want to get my boat in the water!
Kermit
posted 04-23-2000 12:54 PM
First, do you have the spray equipment? If not, what will it cost
you to buy/rent?
B. Have you thought about the hassle and expense of masking?
III. Have you thought about the cost of the above compared to just
hiring it done?
I used to spray furniture and cabinet finishes, and I hated it.
[This message has been edited by Kermit (edited 04-23-2000).]
thechemist
posted 04-23-2000 01:03 PM
HVLP will have the highest transfer efficiency. Airless will send a
spray mist everywhere. Rolling may put either a LOT of bubbles or a
LOT of roller fuzz in the coats. Foam brushes tend to filter out
debris but now we're back to brushing. I'd recommend HVLP. You can
buy a decent rig through Grainger's.
The thinner will have to be something fast-evaporating. You will
likely want to use V M & P (Varnish Maker's and Painter's) naptha,
which is a fairly fast evaporating aliphatic hydrocarbon. White Gas
can also be used. That is gasoline without the additives,
non-evaporating stuff. White gas is sold here-and-there for lantern
or stove fuels, as I recall. Do not confuse it with denatured ethyl
alcohol, also used for such liquid fuel applications. Denatured
alcohol is not a suitable spray solvent for varnish.
Since varnish air-cures, and the lower coats do not cure readily
when buried under a lot of other coats, apply one coat a day, maybe
two mils wet film thickness. That should be 80 percent cured the
next day and another coat will stick fine. Soft to the fingernail is a good indication of incomplete cure. Sanding should be unnecessary
and a fresh coat will bond well to a partially cured coat and small
dust particles will be encapsulated invisibly in the layers. A
final sanding with 2000 to 4000 grit on a hard pad, JUST BARELY
enough to sand flat the tops of the peaks of any bits of final
debris, gives a final appearance indistinguishable from perfect
gloss at more than a few feet.
Jamie Hascall
posted 04-23-2000 05:04 PM
Chemist,
One of your points in your previous answer raised a question that
has also been part of the varnish thread. This involves the issue of lower uncured layers not drying properly when overcoated with new varnish layers. The subject of hot coating varnish came up on the varnish thread. The instructions I had mentioned there which had been given by another respected forum member, spoke of applying up to five coats in a day, and had the feel of good experience behind them.
I was planning on using this method but am now wondering what
the down sides are to applying varnish to teak in this fashion. Any
illumination you can provide would be appreciated.
Jamie
(I don't mean to hijack the thread but hope this helps the cause of
good varnishing.)
[This message has been edited by Jamie Hascall
Charlie Santi
posted 04-23-2000 07:36 PM
I spray varnish often. I use a DeVilbis touch up gun, 50 lbs of air
pressure, a good air dryer. I use Valspar marine spar varnish cut
25% with their marine thinner. I spray one coat a day for a week no
sanding. Let it dry for a week, light sand with 220 and spray on one more even coat.
thechemist
posted 04-23-2000 08:51 PM
I have actually varnished something ... a sixty-year-old Laboratory cabinet with wood drawers an one of those old-style acid-resistant tops...and I put on a few coats too thick. It took a couple weeks for that area to get reasonably hard to the fingernail whereas other areas that had one thin coat a day for a few days gave an overall film thickness that hardened much more quickly. The varnish used was a ten-year-old can of some not-commonly-known brand...I forget what.
The issue of film thickness revolves around driers...what kind and
how much may be in the varnish...and the fact that the curing of
varnish...real varnish...made from oilseeds...not some misnamed
thing...is a chemical reaction between the double bonds in the oil
and the oxygen in the air, catalyzed by a metallic soap called a
drier (because it dries the film). Used to be lead napthenate was
used. good stuff. gave a reliable cure. (seems I wrote this
before...go search for a thread with lead, cobalt, manganese in
it...). Then along came the merchants of fear, with their "it is
all equally hazardous, no matter how much or how little of it there is there" garbage and the people, confused and now afraid, vote for the next wave of nonsense. Proposition 65 passed in California...it says anything on the list of 327 (or whatever number it is ) of
"chemicals known to the State of California" to cause (you don't
want to know...but that list has lead arsenic nerve gas (yes,
actually nerve gas!) and a few other things) chemicals is hazardous
at any concentration down to the limit of detection and then it
magically ceases to be hazardous at all. If science improves the
detection limit it suddenly becomes hazardous again.
that got me going.
I feel better now.
There are top driers and through driers, interestingly enough. A top
drier will cure a varnish film on the top, but not below the
surface. Too thick a film and the stuff will cure on the surface,
wrinkle and stay gooey below. A through drier will cure varnish
below the surface but not on the surface. Has to do with the oxygen
concentrations at which they work or are inhibited. This applies to
enamel paints of the sort made with such resins and a bit of
pigment, also.
Lead is both a top drier and a through drier. When lead got a bad
name (mind you, it was only bad lead in paint. It was good lead in
gasoline. Lot more money in the oil companies and the auto
manufacturers than in the paint companies. Not that I don't
appreciate a good piece of Detroit Iron, myself...I drive a '67
Fairlane fastback...289, 4-barrel and a hot cam, heh, heh. The next
project is to restore the '67 Fairlane ranchero in the back yard.
Got a big block there....390. giggle.
But, I digress.
Lead in varnish was replaced with cobalt, which is a top drier, and
manganese, which is a through drier. Manganese has a bit of a brown
color to it, so sometimes auxiliary driers such as zinc, zirconium
or others are used. Depending on how much top drier and how much
through drier and which ones are in the particular varnish formula,
there is a different chemical curing profile for the film.
Now we get to the dark side of the paint business. These companies
employ humanoids. Not just any humanoid, but the ones from planet
earth. Yes, I know what you have heard about them and it is all
true. You give them some instruction and you have no idea what they
will actually do. Sometimes they add the correct amount of the
correct ingredient, sometimes not. Then there is the mixing issue.
When a gallon of something is thrown into a five hundred gallon
tank, how long does it have to mix to a uniform concentration? That
depends on the time of day and how long it will take to package it
and how long to quitting time and a few other similar factors. The
stuff you get in the can will sometimes be what it is supposed to be
but occasionally will have to much or too little driers in it, due to those factors.
Thus, someone can get one result with one brand at one time, and
someone else can get a different result another time with another
brand or even the same brand. What works with many applications of
the same product bought at different times and places is usually
safe to generalize from...for that particular product. If you find
two brands that behave similarly in drying characteristics, you can
(cautiously ) generalize that far. Single experiments have many
variables. A wet film thickness gauge is the only reliable measuring tool when talking about film thicknesses, number of coats
(Note: There is no definition for the thickness of a "coat"
otherwise) and getting really scientific and reproducible results.
Five coats brushed one-on-top-of-another might add up to
two-and-a-half mils film thickness... as might one brushed coat by
someone else with different reducer quantities, warmer weather
(those resins lose viscosity quickly with increasing
temperature...affects the viscosity and film buildup rapidly,
especially if they used some fast-evaporating solvent in the
varnish...too many variables, do you see?
Everyone can be right sometimes with some products under some
weather conditions, and if no one tries to dent the varnish film
daily with the fingernail to estimate state of cure, implying
waiting time before it can take some mechanical stress, we don't
know how long it takes for that one to cure to where we won't damage the film with a slight bump of something. There are meters that mesure film hardness, but they cost a few hundred dollars and are not readily available to the average varnisher. Without a wet film thickness gauge we really have no idea how thick a film was put on an so reproducible experiments are difficult.
there are 231 cubic inches in a gallon of anything. If a quart of
material has a fifty percent solids content and is spread over about five hundred square feet you will get a one-and-one-half mil dry film thickness. Ten coats over fifty square feet gives fifteen mils dry film thickness. That is a fact and can be used to relate film thickness in different applications and establish some common ground for comparing varnish applications. Hope that helps.
Ed Harrow
posted 04-23-2000 09:53 PM
HVLP? High Volume Low Pressure? Joe, some claim to have excellent
results using a roller and tipping with a brush. My results from the one time I tried it were mixed at best. Read Rebecca Whitman's
book on varnish application for more information on the technique.
Can't use just any roller. Ed
Paul Frederiksen
posted 04-23-2000 11:58 PM
This is why I hang out here. Thank you Chemist.
Joe Murli
posted 04-23-2000 12:34 PM
I have a LOT of varnish to put on. It's a 39' Ketch with a mahogany
cabin house. Has anyone had any experience with spraying varnish?
Can I use an airless sprayer? HVLP? How about rolling?
Help, I want to get my boat in the water!
Kermit
posted 04-23-2000 12:54 PM
First, do you have the spray equipment? If not, what will it cost
you to buy/rent?
B. Have you thought about the hassle and expense of masking?
III. Have you thought about the cost of the above compared to just
hiring it done?
I used to spray furniture and cabinet finishes, and I hated it.
[This message has been edited by Kermit (edited 04-23-2000).]
thechemist
posted 04-23-2000 01:03 PM
HVLP will have the highest transfer efficiency. Airless will send a
spray mist everywhere. Rolling may put either a LOT of bubbles or a
LOT of roller fuzz in the coats. Foam brushes tend to filter out
debris but now we're back to brushing. I'd recommend HVLP. You can
buy a decent rig through Grainger's.
The thinner will have to be something fast-evaporating. You will
likely want to use V M & P (Varnish Maker's and Painter's) naptha,
which is a fairly fast evaporating aliphatic hydrocarbon. White Gas
can also be used. That is gasoline without the additives,
non-evaporating stuff. White gas is sold here-and-there for lantern
or stove fuels, as I recall. Do not confuse it with denatured ethyl
alcohol, also used for such liquid fuel applications. Denatured
alcohol is not a suitable spray solvent for varnish.
Since varnish air-cures, and the lower coats do not cure readily
when buried under a lot of other coats, apply one coat a day, maybe
two mils wet film thickness. That should be 80 percent cured the
next day and another coat will stick fine. Soft to the fingernail is a good indication of incomplete cure. Sanding should be unnecessary
and a fresh coat will bond well to a partially cured coat and small
dust particles will be encapsulated invisibly in the layers. A
final sanding with 2000 to 4000 grit on a hard pad, JUST BARELY
enough to sand flat the tops of the peaks of any bits of final
debris, gives a final appearance indistinguishable from perfect
gloss at more than a few feet.
Jamie Hascall
posted 04-23-2000 05:04 PM
Chemist,
One of your points in your previous answer raised a question that
has also been part of the varnish thread. This involves the issue of lower uncured layers not drying properly when overcoated with new varnish layers. The subject of hot coating varnish came up on the varnish thread. The instructions I had mentioned there which had been given by another respected forum member, spoke of applying up to five coats in a day, and had the feel of good experience behind them.
I was planning on using this method but am now wondering what
the down sides are to applying varnish to teak in this fashion. Any
illumination you can provide would be appreciated.
Jamie
(I don't mean to hijack the thread but hope this helps the cause of
good varnishing.)
[This message has been edited by Jamie Hascall
Charlie Santi
posted 04-23-2000 07:36 PM
I spray varnish often. I use a DeVilbis touch up gun, 50 lbs of air
pressure, a good air dryer. I use Valspar marine spar varnish cut
25% with their marine thinner. I spray one coat a day for a week no
sanding. Let it dry for a week, light sand with 220 and spray on one more even coat.
thechemist
posted 04-23-2000 08:51 PM
I have actually varnished something ... a sixty-year-old Laboratory cabinet with wood drawers an one of those old-style acid-resistant tops...and I put on a few coats too thick. It took a couple weeks for that area to get reasonably hard to the fingernail whereas other areas that had one thin coat a day for a few days gave an overall film thickness that hardened much more quickly. The varnish used was a ten-year-old can of some not-commonly-known brand...I forget what.
The issue of film thickness revolves around driers...what kind and
how much may be in the varnish...and the fact that the curing of
varnish...real varnish...made from oilseeds...not some misnamed
thing...is a chemical reaction between the double bonds in the oil
and the oxygen in the air, catalyzed by a metallic soap called a
drier (because it dries the film). Used to be lead napthenate was
used. good stuff. gave a reliable cure. (seems I wrote this
before...go search for a thread with lead, cobalt, manganese in
it...). Then along came the merchants of fear, with their "it is
all equally hazardous, no matter how much or how little of it there is there" garbage and the people, confused and now afraid, vote for the next wave of nonsense. Proposition 65 passed in California...it says anything on the list of 327 (or whatever number it is ) of
"chemicals known to the State of California" to cause (you don't
want to know...but that list has lead arsenic nerve gas (yes,
actually nerve gas!) and a few other things) chemicals is hazardous
at any concentration down to the limit of detection and then it
magically ceases to be hazardous at all. If science improves the
detection limit it suddenly becomes hazardous again.
that got me going.
I feel better now.
There are top driers and through driers, interestingly enough. A top
drier will cure a varnish film on the top, but not below the
surface. Too thick a film and the stuff will cure on the surface,
wrinkle and stay gooey below. A through drier will cure varnish
below the surface but not on the surface. Has to do with the oxygen
concentrations at which they work or are inhibited. This applies to
enamel paints of the sort made with such resins and a bit of
pigment, also.
Lead is both a top drier and a through drier. When lead got a bad
name (mind you, it was only bad lead in paint. It was good lead in
gasoline. Lot more money in the oil companies and the auto
manufacturers than in the paint companies. Not that I don't
appreciate a good piece of Detroit Iron, myself...I drive a '67
Fairlane fastback...289, 4-barrel and a hot cam, heh, heh. The next
project is to restore the '67 Fairlane ranchero in the back yard.
Got a big block there....390. giggle.
But, I digress.
Lead in varnish was replaced with cobalt, which is a top drier, and
manganese, which is a through drier. Manganese has a bit of a brown
color to it, so sometimes auxiliary driers such as zinc, zirconium
or others are used. Depending on how much top drier and how much
through drier and which ones are in the particular varnish formula,
there is a different chemical curing profile for the film.
Now we get to the dark side of the paint business. These companies
employ humanoids. Not just any humanoid, but the ones from planet
earth. Yes, I know what you have heard about them and it is all
true. You give them some instruction and you have no idea what they
will actually do. Sometimes they add the correct amount of the
correct ingredient, sometimes not. Then there is the mixing issue.
When a gallon of something is thrown into a five hundred gallon
tank, how long does it have to mix to a uniform concentration? That
depends on the time of day and how long it will take to package it
and how long to quitting time and a few other similar factors. The
stuff you get in the can will sometimes be what it is supposed to be
but occasionally will have to much or too little driers in it, due to those factors.
Thus, someone can get one result with one brand at one time, and
someone else can get a different result another time with another
brand or even the same brand. What works with many applications of
the same product bought at different times and places is usually
safe to generalize from...for that particular product. If you find
two brands that behave similarly in drying characteristics, you can
(cautiously ) generalize that far. Single experiments have many
variables. A wet film thickness gauge is the only reliable measuring tool when talking about film thicknesses, number of coats
(Note: There is no definition for the thickness of a "coat"
otherwise) and getting really scientific and reproducible results.
Five coats brushed one-on-top-of-another might add up to
two-and-a-half mils film thickness... as might one brushed coat by
someone else with different reducer quantities, warmer weather
(those resins lose viscosity quickly with increasing
temperature...affects the viscosity and film buildup rapidly,
especially if they used some fast-evaporating solvent in the
varnish...too many variables, do you see?
Everyone can be right sometimes with some products under some
weather conditions, and if no one tries to dent the varnish film
daily with the fingernail to estimate state of cure, implying
waiting time before it can take some mechanical stress, we don't
know how long it takes for that one to cure to where we won't damage the film with a slight bump of something. There are meters that mesure film hardness, but they cost a few hundred dollars and are not readily available to the average varnisher. Without a wet film thickness gauge we really have no idea how thick a film was put on an so reproducible experiments are difficult.
there are 231 cubic inches in a gallon of anything. If a quart of
material has a fifty percent solids content and is spread over about five hundred square feet you will get a one-and-one-half mil dry film thickness. Ten coats over fifty square feet gives fifteen mils dry film thickness. That is a fact and can be used to relate film thickness in different applications and establish some common ground for comparing varnish applications. Hope that helps.
Ed Harrow
posted 04-23-2000 09:53 PM
HVLP? High Volume Low Pressure? Joe, some claim to have excellent
results using a roller and tipping with a brush. My results from the one time I tried it were mixed at best. Read Rebecca Whitman's
book on varnish application for more information on the technique.
Can't use just any roller. Ed
Paul Frederiksen
posted 04-23-2000 11:58 PM
This is why I hang out here. Thank you Chemist.