Hello Botsmaker,

The product is not defective. Water tends to evaporate naturally from any given solution and since the salts within hydroponic liquid fertilizers are concentrated they tend to crystallize as some solution evaporates from the bottle. If you take too long to use the whole bottle you could indeed be losing the homogeneous character of the solution as some salts might have a lower solubility than the rest and they may separate themselves out efficiently as time goes by.

The best thing here to do to guarantee that you are adding a homogeneous solution is simply to add distilled (NOT RO!) water until the crystals redissolve, then adjust your EC as you usually do with the solution. This way you will not be changing the overall ratios of nutrients within your solution over time.

This are my two cents as a chemist :o) I hope this helps !

Best Regards,

Daniel

Here is a link that might be useful: Everything Hydroponics

Always good to have a chemist's two or three cents!
Well, some manufacturers put it simply that way: "our products are concentrated to the limit of saturation. In case visible crystallization occurs that will not disappear with shaking, mix the entire content with the equal amount of hot water and double the amount used".

Actually one should add a drop more, as at least some water has evaporated. But this might not fit a KISS concept and "irritate" the reader unnecessarily and is probably left out by manufacturers. Well, at least this way of proceeding could come handy if no instrument is available.

I divided the solution with another gallon of bottled water. Now I have 2 gallons of VF-11 at half strength. The precipitate did dissolve a bit more. Still have some separation and will just have to live with it. I've had some experience with chemistry and would really like to make my own. Years ago I experimented with periodic precipitation and grew crystals in gels. Raw chemicals are not so easy to come by like they were years ago.