We are advised to add canned carbon dioxide to prevent oxygen from polimerizing the top layer of varnish. Why not use propane, which ,as a member of the parafin series of hydrocarabons is quite inactive chemically unless heated, and which is readily available in every workshop? I do not say this lightly, having anesthetised many people for surgery using a form of propane(cyclopropane). I’m dating myself, as cyclopropane hasn’t been used in medicine for over forty years. Elaborate precautions were then in place, as it was used mixed with oxygen.
Tom
Replies
Tom,
Is propane heavier or lighter than air? I think the answer to that will largely determine propane's suitability.
Alan
Propane is heavier than air.Howie.........
You can use any inert gas to displace the oxygen. Oxygen displacement is the key thing.
Now this was a few years ago, LOL, but Uncle Dick used marbles...
Ed's comment about marbles is a good one, and one that's ignored by most of us. It used to be (& maybe still is) standard practice for photofinishers to fill their developer bottles with marbles to bring the liquid up to the top of the container. Developer is also subject to deterioration by oxygen, and marbles are cheap, inert & very effective.
ROTFLMHO, I'm used to being ignored, you can even ask our dog (actually, around here he's about the only one who might listen to me ;-) )
Then, of course, there was the wag who, when he saw a handful of marbles in my can of varnish commented, "Hmmmm, now I know where all your marbles went, and more is the pity that there were so few."
A simple solution I use is to nail holes around the perimeter of the can, allowing drainage of the finish and easier closure of the lid.
I think the explosion hazard is likely minimal. Would be way above the explosive mix concentration until opened. Propane from a torch will work and also Co2 from a photographic Dust off product. Both are cheaper than "bloxygen". I don't know if or why that stuff is better, other than its inert.
Propane -- seems mighty risky to me -- although I have never set a match to Bloxygen to see what would happen. Maybe you could try it yourself and report back here with the results :o)................
Re: holes in the lip. I keep a 10p nail around and drive 3 holes in the lip of every new can. Unfortunately, this does not prevent a skin from forming; but it does allow you to wipe out the lip, keeping dried gunk from forming and dropping into your varnish (or paint).
The holes are a good idea if you are going to use the finish quickly. The actually decrease the air seal of the can. We tried this out in the shop I used to be involved with and the material lasted much longer in the cans that did not have the drip holes.
Of course, the material you are going to use should be poured into a separate container and the paint can closed as quickly as possible. And, never pour unused material from you working can back into the original container. Not only has the working material begun to cure, it has picked up dust and gunk as you worked with it.Howie.........
Any petroleum or alcohol based finish in a can would already have a potentially explosive air and vapor mix in the can's headspace, adding propane wouldn't make the chance of an explosion any more likely. Being I've never heard of this happening it would seem that the chance of an explosion is very remote.
John W.
How do you go about getting propane into a half empty (full) can of varnish?
Frank
Turn the torch on and aim into the can.Propane is heavier than air and will sink...
BTW, I don't advocate using propane to prevent polyurethane from skinning.
Edited 8/16/2004 3:14 pm ET by JACKPLANE
Why not?
I've had a bad experience with propane years ago, and don't like using it for anything except cooking when I go camping.
I like being a happy camper.
About the time I saw this thread, I was working with some oil based paint, and thought, why not try the propane?
I had a half can of white semi gloss. I shot propane into it (gently), until I could clearly smell it a few feet away. I sealed the can, and set it aside.
I had occaision to use some of the paint today, and found it pretty skinned over.
I have been using Bloxygen in gallon cans of Waterlox for a few months now, and have had no skinning at all in the Waterlox.
Maybe there's a trick to the propane?
I use a process that's been around since before mud was invented, and it works very well. Just secure the lid tightly and turn the can upside down. I have kept finishes for years using this method.
I heard about that technique too. Tried it once with a can of poly, and got the worst awful mess you could imagine -- since a skin formed on the top of the can (which of course was the bottom once you turned the can upright).
Did I do something wrong? As I recall, only one third of the poly remained -- which probably meant there was just enough air to permit skin formation.
I have never had the problem you describe, but it may be associated only with poly. Since I don't use poly, I can't speak to it. Somebody who is better versed with the chemistry of finishes may be able to answer this.
like all the others I have tried all except the propane and if my present method doesn't work -propane will be next - because I have had to dispose all the old cans of varnish I am down to one can of Prat and Lambert 42 and it is sitting right out on my work bench and almost every day I pick it up and shake it-- I am going to shake it twice just before I go to Atlanta-- in 2006 I'll let you know if it works
Shaking the can daily just stirs the polymerizing surface layer into the rest of the varnish contaminating all of it, I'm not exactly sure what the long term result would be, but it probably won't be good.
My solution to the problem is to transfer the bulk varnish or oil into small mason jars, filling the jars almost to the brim so there is little oxygen to react with. Using this technique I can get through an entire gallon of highly reactive Waterlox with no loss other than a bit of skin forming on the partially emptied "working" jar.
John W.
You know the solution to this problem - pack it in boxes, like the boxed wine. The varnish would be in a flexible bladder, and the volume of the bladder would decrease (sort of, anyway, ;-) ) as the wine, I mean varnish was drained. Seems like a simple solution, and easier than Poppie's (or was it Uncle Dick's) marble trick. (Which does work, by the way).
I think the bladder idea is terrific (really). Why don't you invent something that will work and is convenient to use?
I know a patent attorney :0)..................
But maybe the best idea came from Vern -- powdered varnish (and paint). How about the powder in one can, and a proprietary concoction of chemicals in another (which will not skin over) -- kind of like that old urea formaldhyde glue.
Nikkiwood - I think the downside to the concept is bubbles. It would seem to be a great bubble inducer - perhaps running the varnish thru a filter (normal practice) would help keep that problem undercontrol, I don't know. Besides, I was taught by masters to use marbles, and who am I to question them. ;-)
Not to be taken as anal, but I don't pour varnish from the can, I dip it out using a small, unwaxed cup. No bubbles, even if I don't use a strainer (ssshhhhhhh....)
nikkiwood- it has been said that neccessity is the mother of invention-- and what could be more neccessary than a nice fresh mixture of varnish when you ready to shoot your silky smooth cherry piece-- and notice I said shoot( bubbles are not a problem) you want to make a million -- you invent and I'll test it--deal?making sawdust
I think that when all the oxygen has been tied up the product will stabilize and about then I will forget to shake it and the skin will form-- I tried the marble method and ended up with such a mess I through everything out-- what happens to plastic if you put the unused varnish in a zip-lock baggie-- I think reducing the size of the storage container is the best solution0-- why don't you invent a powder varnish and then we would just add turp and use what is neded!making sawdust
those food saver vaccums are really ideal for finishers. You can transfer varnish and other finishes to smaller jars and vacuum seal them with that little bugger. Shellac flakes can be put in small baggies and vaccum sealed keeping humid air out of the flakes contact. You could actually just place your varnish cans into the bags and seal them up, preventing accidents to fallen varnish cans that the lids jump off trying to save themselves from a dent.
Long term hand tool storage: place your iron or even router bits into a baggie and vacum seal them up to keep rust off of them. The bags are resealable and reusable so if you use an iron tool only a few times seal it up, keep it from rusting.
In a bind you could probably use it to veneer small items.
If youre an outdoorsperson, heck you can always have some dry clothes or dry matches.
They really are nifty little things those food saver vacuums.
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