So I'm fairly new to this whole thing and my searches of the google
archives haven't turned up much. I'm sure I need some help with the
terminology more than anything, but I'll ask the question again (I'm
sure it's been asked before) anyway.
I have a couple of different cans of varnish that I opened and dispensed
into smaller containers for use. Now the varnish has hardened in all
the various conatiners, whether sealed or not. I know it has to do with
reaction to the air, but I don't know how to prevent it. I've seen a
couple threads that I think suggested adding some other chemical to the
can that wouldn't mix with the varnish but would displace the air.
So my first question is basically, how do you prevent your varnish from
kicking to a hard molasses substance. What should I do once I've
separated the actual amount I want to use from the main can?
My second question has to do with thinning. I've read somewhere to thin
with mineral spirits or something similar. What are the benefits of
doing this? I've used the varnish straight and love the finish and I
haven't had any real difficulty in application such as bubbling or
anything. Are there benefits to thinning that I'm not aware of?
My final question (for now) also has to do with thinning. Is it
possible to thing varnish after it has become the molasses substance I
described in my first problem?
Thanks for any and all pointers (especially links to places I can do
The easiest way to keep the top from skimming over is to store thc
containers upside down. There is an inert gas that you can add to the top
of the varnish in the can to displace the air in the can that helps slow the
curing process in side the can. Bloxygen is the retail name for the gas.
Kicking? Not a wood working term.
What should I do once I've
Tyoically you want to seperate Paint from the can it comes in, You want
room inside the container so that you can tap the sides of the brush against
the inside sides of the can after loading the brush. Typically you want
paint to go on fairely thick and typically in 1 coat. Tapping the brush vs.
scraping against the top opening of the can leaves more paint on the brush.
Varnish is another matter. Typoically you want to put on several Thin
coats. Draging you brush across the inner top opening of the can prevents
the brush from loading too much varnish. Leave the varnish in its original
Do this ONLY if you are using an oil based varnish and if the varnish seems
to dry too quickly before flowing out.
Adding a "thinner" helps the varnish flow off the brush, helps prevent brush
drag, and helps the materal level out after being brushed on. DO NOT over
brush. Additionally when using oil vased paints or varnishes add a trace
amount of a "thinner" to the clean brush before using. This will help with
cleanup and helps with the material flowing off the brush.
I've used the varnish straight and love the finish and I
If you are not having problems don't try to fix a problem
Once it has reached that state I toss the stuff in the trash can. Do not
buy more that you would use in a 6 to 12 month time.
Kicking is what epoxy does when it hardens. The varnish I am using is
acting like that...it's not getting a thin film on the surface, the
whole can is hardening and turns into something like amber. It looks
really cool, but isn't very useful to me now.
I'm not sure what you thought I meant, but I've always been told to
separate varnish from it's original container unless you expect to use
it all. I don't use paint at all, at least not on wood, yet. The
mechanics of actually doing the application I've got down pretty good.
What I meant was, what should I do with the main varnish can...add
something to it, just close it up and try to seal it tightly, or
something else entirely?
This is good information, thanks a lot. I think I'm using a water based
varnish, but I'm not sure. I'll have to check it out.
I'm not trying to fix a problem, I'm trying to find out if there are
benefits I'm unaware of. I'll decide for myself if those benefits are
worth the added work. I'm just looking for as much information as I can
get so that I can make the most informed choices in the work I do.
These cans of varnish were maybe a pint or at most a quart. They should
last me through a couple of my larger projects at most so I didn't have
too much and let it sit for a long time. In fact, I only had them for a
week or or two before I used them but one of them hardened in a week or
so after I opened it (and closed it immediately after pouring what I
needed into a separate container) and the other took maybe two weeks.
At the prices I'm paying for this varnish, I'd rather not have that
happen as they seem completely unusable to me at this point.
Well, IMHO it is all curing if it is hardning. IMHO dump it and get new
Not a bad practice but I have never done this, at least in the last 27
years. It would save you from having to haul around a larger container if
you buy large quantities.
I don't use paint at all, at least not on wood, yet. The
I would not recomend adding anything to the varnish to mix with the varnish
untill you are ready to use it. I would however add the Bloxygen gas on top
of the product inside the can to help prevent curing inside the can.
Look at the clean up directions. soap and water, thin with water, Clean up
with mineral spirits, thinner, thin with a those items.
Adding a thinner will help the product flow out evenly on the surface and
helps to prevent bubbling. Varnishes difer greatly in viscosities. Some
require adding a thinner for best results. Better brands like General
Finishes are typically ready to go right out of the can.
Also don't discount a decent quality FOAM brush. These brushes do great job
of puttind down varnish. Be sure to buy the better foam brushes that will
permit use with oil based finishes.
In fact, I only had them for a
I have had varnishes that were old to start with do that. Read that as they
sat in the store toolong. Perhaps they had been opened and reclosed.
Again, go with the better brands and this should not be a concern expecially
in that short period of time.
I factor in spending at least $15 per quart for varnish. Buy smaller
containers of the product if you are not going to use it within several
months. Remember that $10 extra for the good stuff is cheap compared to the
materials and time that you put into the project.
Something else to consider, If the surface does not have to be a thick
protective one and you are going for a Satin finish, gel varnishes are a
dream to apply and you get a glass smooth hand rubbed look. Apply with an
old t-shirt or cheap brush and after a few minutes wipe it off with a clean
lint free cloth. The big advantage to gel varnishes is that dust is never a
problem. Immediately after wiping with the cloth to remove the excess the
surface is "almost" dried enough to touch.
One of the oldest tricks going is to displace the air in the can with
Simply point an unlit propane torch down at the top of the can for a
couple of seconds before replacing can lid.
Propane is heavier than air so it will settle on top of the varnish.
On Thu, 03 Mar 2005 18:20:38 +0000, Lew Hodgett wrote:
Idea just occurred to me, never tried it: wrap a finger around the air
holes at the back of the nozzle when you fill the jar with propane. No
sense mixing in additional atmosphere, right? Also, the valve should be
open just above a trickle so you don't entrain too much atmosphere. If
we're very lucky, we might see enough Schlieren effect to tell when the
jar's full of propane.
"Keep your ass behind you"
vladimir a t mad scientist com
Either displace the oxygen with "bloxigen" or similar, or transfer the
remaining finish to a sealed container about the same size a the volume of
finish to be stored.
Less material being applied at a time. Drips will be less of a problem and
the resilting finish will be more even, but it will take more passes (time)
to get a similar "build".
If it give you results with which you are happy, stick with it.
No. When varnish cures, it undergoes a chemical reaction with oxygen which
is (for the most part) unreversable. This is unlike shellac or lacquer which
"cures" by evaporation and can be later "melted" with the original solvent.
If you have a skin on the varnish, you can strain out the solids and get
some more milage out of it, but that is probably a bad practice for other
than "quick & =dirty" work.
Speaking personally, I do it by not using polyurethane. I don't use
many varnish or varnish-like materials and those I do use are spirit
varnishes (plant resins in alcohol) or shellac. Plain solvent
varnishes like this don't suffer from the skinning problem. The one
poly I do use is Patina, a gel. This comes in fairly small tins and I
generally use them until they skin badly, then dump them. The tin size
is such that this isn't a big waste - about once a year.
You can (depending on the solvent base of the 'varnish') lay a layer of
plastic film on top of the liquid to prevent contact with oxygen.
Thin following package directions only. If thinning is a reasonable thing
to do, the package will suggest a reasonable quantity and a specific type
of solvent to be used. Trust the manufacturer on this. As others have
noted, thinning affects handling and drying characteristics. One use of
thinning is to apply a thin layer as a grain sealer to limit the
absorption of the normal layer. When the quantities are small, the
dollar amount of the varnish saved often isn't worth the effort of the
You can break off the crystallized surface and re-thin the molasses but
it probably won't return to its original chemistry and thus won't give
its original results. Try it on a piece of scrap before committing it
to a 'for the marbles' project. FYI, I just buy the smallest container
when trying a new finish and that lets me make the judgment call about
buying a larger quantity.
As others have mentioned, it's the oxygen in contact with the varnish
that's causing it to cure in the can. You need to:
a) eliminate as much oxygen as possible by replacing it with an inert
gas like nitrogen, propane as others have suggested tho I've never
tried, or a commercial product like Bloxygen.
2) reduce the amount of oxygen containing air in the container by either
squeezing the sides of the container before capping, putting inert
marbles (glass fer instance) in the varnish to increase the material
volume, or pour into smaller container so that it's full before capping.
III) place a non-reactive material on the surface of the varnish to
isolate the oxygen from the varnish. This can be a layer of plastic wrap
or a few tablespoons of solvent like mineral spirits. If you go the
solvent route, gently spoon it on the surface and you don't want to
shake the can afterwards or else you'll lose the barrier pool on top.
four) use a Seal-a-Meal type device to pull a vacuum on the container to
eliminate as much air in the can as is reasonable.
Other considerations are to ensure the lid is sealing properly to the
container. Metal distortion or cured finish build up on the rim or lid
will cause gaps to allow the entry of air into the container. If you
store the can upside down - and assuming the gaps are small - the finish
will seal the air leaks and stop infiltration. In addition, any finish
that cures at the now "top" of the can will end up on the bottom when
you right it and uncap for use.
You might also buy your varnish in the smallest sizes possible. Paying
less per ounce by buying large sizes ain't a savings if you're throwing
away half of it anyway.
Time honored technique. You can also buy smaller cans of every size from
local places that mix up paint. Paint stores (maybe even the BORGs... not
sure), certainly automotive paint stores - these guys mix up quantities of
paint from 1/2 pint to 1 gallon every day and have all kinds of unlabeled
cans and tops on hand. Pour off your partial gallon into quart cans and
stack them on a shelf.
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