The well known and highly regarded artist Bill Martin has a great idea about how to save your Canada Balsam…
Don’t waste even a dram of your precious Canada Balsam. When my Canada Balsam becomes low in its container, it often begins to get a bit sticky, and gummy. When this occurs, it won’t pour any more. To make it more liquid, and manageable once more, I add a few drops of Oil of Spike Lavender to it, and I stir it around in the container with a palette knife. I mix it until it becomes more liquid again, and pourable. There is so little Oil of Spike Lavender in it that you can still measure it into a container for your medium recipe as if it were only Canada Balsam, ignoring the small amount of Oil of Spike Lavender that you’ve added.
When you have mixed it enough so that it is pourable, then just measure out the amount you need into your container, and you’re ready to go. And, then you are also ready to open a fresh container of Canada Balsam, the next time you need to mix your medium.
And…..To get even the last few drops of the Canada Balsam out of its container, just swish a little more Oil of Spike Lavender around in the capped container, and then pour it out into your measuring container, this time considering the measurement to be “Oil of Spike Lavender”. Top off the measurement, to complete the quantity with pure Oil of Spike Lavender, and stir the entire contents in the measuring cup, using a palette knife.
Pour the mixed contents into your “holding bottle”, or “medium reservoir”, and you’re good to go for several more paintings.
Another hint: After opening your fresh container of Canada Balsam, and removing some, just blow your breath into the container immediately before capping it back up. It is the oxygen in the air that causes resins to develop a skin over their surfaces, and exhaled breath contains more carbon dioxide than oxygen, thus helping to protect the surface from becoming stiff, and gummy when the quantity becomes very minimal in the container.