Saving Paint and Varnish

Ahoy All, for some time now, I have been saving my left-over paint and varnish, after I open a new can ,to use another day.

The paint and varnish used to skim over and get a crust on the left-over liquid in the can.

I can avoid this skim-over by decanting propane gas from my un-lit propane gas torch, into the can and carefully replacing the lid.

Over time I have noticed that the cans that were preserved that way, would try to collapse inward. Could it be that the propane gas is being absorbed into the paint or varnish and thus creating a vacuum inside the cans ?

Now I have a problem with the catalyser of the two pack Intl Paint, LPU “Perfection”, which the catalyser goes hard and you can not purchase just the catalyser by itself, at least not here in Singapore.

So does anyone have an idea of how to extend the shelf life of the two part catalyser after the can has been opened ?



The simple chemistry rule that like dissolves like applies to propane and hydrocarbon solvents. The propane dissolves into the hydrocarbon solvents used in the paint and varnish resulting in a partial vacuum within the sealed can. The dissolved propane will evaporate with the solvents when the paint or varnish is applied to a surface and will not affect the paints properties.

The isocyanates in LPU paints are moisture sensitive. The catalyst most likely contains hexamethylene diisocayante (HMDI), HMDI polymers and solvents. The HMDI and HMDI polymers will react with moisture to form an amine which then reacts with the HMDI and HMDI polymers to form a linear polyurethane plastice type product. Unless you can open the can of catalyst and dispense the amount you need in a moisture free environment, the self-life of the catalyst will be limited once the can is open.

The manufacturer of the LPU may be able to make suggestions to extend the shelf-life of the catalyst after the can is opened.


I bought two cans of Bloxygen at a woodworking trade show years ago.You spray this under the partially opened lid of your used can of varnish, seal the lid and it prevents skimming. I also have stored the partially full cans of varnish upside down.

Bob & Lois

BCC Jolie Brise

Ahoy Rod and Bob , T Y , for taking the time to reply, as your imput is so , helpful !

As Rod could have guessed that Propane Gas is loaded with moisture, and that would not have been good to use to save the 2 pak catalizer of Intl LPU , Perfection.

I did not know about Bloxygen , but will check out it’s availability , here in Singapore , a long shot, that may be !

As times are so very tough, it becomes even more important, to conserve our resources , “In The Can” , before we are required to discard, the remnants, because one of the two-part chemicals, has gone off .

Could it be a whole new field, can be in the making ??? that of how to use every last drop of the very costly products we purchase ???


Bloxygen is a mixture of dry inert gasses that displace the air (oxygen) in an opened can of paint, varish, etc.

The cost for a can is $10 USD.