Question: What happens when your test fluids freeze and then re-thaw, and why are you so concerned with avoiding this when you ship in the winter?
Answer: With regard to how freezing may affect product performance, this is a difficult question to answer, as it comes down to the inability to prove a negative. To start, let me make it clear I am not a chemist by any stretch of the imagination; my background is experimental design and quality control. So, if there are any readers out there who can comment on the chemistry of the freeze/thaw cycle on binary (plus dye) mixtures, I would love to hear from you!
I have heard a number of anecdotal reports of changes in the reactions of surface tension test fluids after they have been frozen, but cannot personally remember ever seeing an effect myself. Nevertheless, subtle changes in the mixtures could have a meaningful impact under some circumstances: Water vapor adsorption could be accelerated; leaching of polymer from the bottle at the liquid/solid interface could be increased; the dispersion of the dye in the 2-ethoxyethanol/formamide mixture could be altered. Undoubtedly a good number of other possibilities exist as well, including the potential for shortened shelf life.
The biggest problem with determining any impact on performance is that to run a comprehensive study on the effect of freezing on test accuracy, you would need to test at least a dozen different dyne levels on an almost literally limitless variety of substrates – a Herculean task at best.
So, in the interest of caution and keeping the anecdotes in mind, I feel it is best to avoid freezing dyne solutions.
But, the most pressing issue with regard to freezing is damage in transit. ACCU DYNE TESTTM Marker Pens will sometimes lose their tip seals and leak during shipping once they have been frozen. I believe that the reason for this is that shrinkage of the plastic spring that controls the release of test fluid from the tip allows seepage of test fluid during the thaw cycle. Sometimes the seal between the pen barrel and the tip leaks for similar reasons. Rarely, the same problem can manifest with bottled test fluids – especially with dropper bottles.
The short and the long of it is that, based on brand stewardship considerations and replacement costs, as well as the potential for effects on measurement accuracy, we feel it is very important to avoid allowing ACCU DYNE TESTTM Marker Pens and surface tension test fluids to freeze.