varnish/oil homebrew mix turned to gel

[Big Rob]

About 9 months ago I mixed a small batch of 2/3 varnish (Behlen's rock hard) and 1/3 pure tung oil. I used it a couple of times this past week and it worked fine -- dried fine and in the can looked like it did when I mixed it back in November. When I opened the can yesterday to put on a third coat, the mix had turned to the consistency of jello. It's in a small (pint), new paint can from a paint store. The can is about 1/4 full.

Any ideas what's happening? Is this normal? The seperate containers of varnish and tung oil that I mixed this from seem to be fine. Neither one of them has turned to gel.

[C & S]

The can is not full enough.

While the can is 1/4 full of varnish it is 3/4 full of air. The oxygen in that air is beginning to cure the varnish.

To avoid jello do one of the following.

1. Pour unused finish into a smaller container
2. Displace air with marbles.
3. Displace the air with Bloxygen (TM) or some other heavier-than-air non-reactive gas and cap quickly.

-Steve

[Fly-by-Night CC]

Yes it's totally normal. Enough oxygen or whatnot from the atmosphere entered the container to overcome the high solvent vapors above the liquid and set off curing. I think you're lucky you got 9 months out of it - but then you must not have opened the container much plus it was well sealed. I've had good success using the jello varnish as a rubbing finish as long as it spreads out under your rag pressure. Apply and wipe off just as you would if it were more liquid-y.

You can buy something called Bloxygen which you spray into the container just before capping which is supposed to eliminate the frequency this occurs. You can also buy a small tank of nitrogen to apply similarly. I just mix small oil and varnish batches and accept the jello state when it happens.

The real heartbreak is when you go to open your 3/4 full can of Rockhard and it IS.

[Dave Balderstone]

1. Buy a few of these...

djb

[Tom Banes]

On Mon, 01 Aug 2005 17:36:12 -0600, Dave Balderstone

These are neat! Wish they made some that startted at 1/4 L and went down!

[Dave Balderstone]

They do have little-bitty ones...

djb

[Juergen Hannappel]

Look in a store that sells photographic lab equipment, most of the chemicals used for processing film also don't like oxygen, so collapsible bottles are a common thing there, and available also in smallish sizes.

[George]

What you recommend is as common as vinyl recordings and typewriters here.

[Juergen Hannappel]

Ok, I rephrase: ...collapsible bottles once were a commen thing there... One would not think at first that the digital camera revoluton has an impact on wood finishing, but as one craft dies out it oulls others also into the grave.

[Dave W]

I have chased this problem for decades trying to save varnish from one year to another. I have tried collaposable bottles (the problem is the threads), freon, propane, marbles (what a mess). I am sold on punching (I use an awl) two small holes in the lid of the can, pouring through the holes and resealing with a #10 sheet metal screw. Inverting the can briefly coats the end of the screw with varnish and makes a good seal. I am convinced that air enters the can through the lid seal after repeated openings. The screw trick works for varnish because stirring or mixing is not needed.

[Glenn de Souza]

Thanks Dave, I like this idea and having battled the same problem for years, I'm going to try it.

In fact, I think I'll try pouring out the quart size can into pint or 1/2 pint cans, using the screw trick as I open each. 1/2 pint cans are like single use sizes.

Glenn

[dadiOH]

container

You can also just take a deep breath, hold it for a few seconds and then breathe into the container. Used to *always* do that with photo developers...the CO2 in your breath is heavier than air and will settle down forming a "cap" over the liquid to be protected.

-- dadiOH ____________________________

dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at

[Fly-by-Night CC]

I had heard of this method but also read a reply that exhaled breath still has a lot of oxygen in it.

[dadiOH]

Yes but the CO2 is heavier and settles.

-- dadiOH ____________________________

dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at

[George]

Sorry, no time to settle, and your breath is about 17% oxygen on exhalation, versus 21 on inhalation, if you believe the physiology folks. Carbon dioxide is maybe 3%, so you can see there's going to be a big difference.

Then there's the water vapor, which isn't a good thing either.

[Australopithecus scobis]

Bumper sticker: Honk if you passed Thermo

[john]

Pure CO2 is heavier, but over time WILL mix with whatever gas is also there, otherwise we would have a layer of close to

100% CO2 right at ground level. Key point is to reduce the amount of oxygen that can get to the homebrew. I weld, so I have a big tank of ARGON and just blow some 99+% argon into the cans and it keeps things from oxidzing GREAT. High concentrations of ANY relatively inert will work, but exhaled breath is NOT going to work - still something like 16% oxygen in that exhaled breath and it WILL cause oxidation, just a tad slower than room air

John

[Roy Smith]

Not to mention that it's saturated with water vapor, which is probably not good for a lot of stuff.

[Dave Balderstone]

In the small containers I have, I just crack the torch open and blow propane into it. So far so good.

[Dave W]

dadioh, It is true that exhaled air has more carbon dioxide than air does. It is true that carbon dioxide is heavier than the other constituents of air. BUT, if you expect the carbon dioxide to "settle out" you will have to wait a long time. Brownian motion and other factors keep the gases well mixed.