Varnish storage...

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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 more research).
bkr
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Snip

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 container.

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.
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Leon wrote:

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.
bkr

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<snip>

What brand and product is on the can?
Some names are deceptive. Waterlox, for example, is not generally water- based. It does have a gelling property, not entirely unlike what you cite.
Patriarch
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I see.
The varnish I am using is

Well, IMHO it is all curing if it is hardning. IMHO dump it and get new product.

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.
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Thanks for the info, Leon. I have been using foam brushes for my varnishing so far and I like the results. I'll probably keep using them.
bkr
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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.
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Yes, it is. Use in a sentence: If you touch my tablesaw, I be kicking your ass!
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"bkr" wrote:

Leon wrote:

One of the oldest tricks going is to displace the air in the can with propane.
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.
HTH
Lew
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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
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Australopithecus scobis wrote:

Beats the hell out of me.
I just put some propane on top, close the lid, and go back to boat building.
Works for me, SO FAR.
Lew
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Don't let it come in contact with oxygen.

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.
Steve
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wrote:

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.
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On Thu, 03 Mar 2005 09:56:27 -0500, bkr wrote:

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 additional coat.

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.

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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.
--
Owen Lowe
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Eeehhhhh... top it off with propane/atmosphere. The propane settles down to the top of the finish, the atmosphere floats on top, away from the product. No reason to turn this into a project.
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Dave Hinz wrote:

I've actually had decent luck with exhaling into the can and quickly closing it.
Barry
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bkr wrote:

I fill the extra space with glass marbles from Toys-R-Us. They're reusable, easy to separate from the varnish, and glass is inert.
Barry
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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.
--

-Mike-
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On Fri, 04 Mar 2005 12:23:13 GMT, B a r r y

Well, that won't work, the empty space is at the top, and the marbles go to the _bottom_. Honestly, Barry, you of all people should have thought of that.
Dave Hinz
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