I keep my drop checker reference solution refrigerated. Does this have any affect when used in a drop checker ? When I mixed the solution up over a year ago it was 4.0 dkh. Now it tests at 3.0.

Did the solution test at 4 dKH when you first mixed it up, or was that a calculated value?

Refrigeration should have no effect at all, but if the container isn't air tight, some water could evaporate, which would raise the KH.

The solution did test at 4.0 when I first mixed it up. I'm going to try a new kh test kit and if I get the same result I'll just mix up a new batch.