I've never heard of this "A and B" stuff. Could you please post your information source?

I build my own nutrient concentrate and all that is covered at my Web site at www.tangreenthumbs.com (nothing for sale!). Feel free to copy what I do.

I've never had any problem with precipitation, other than the fact that I screen all my concentrate through a nylon stocking before injecting it into my storage tank. This separates all the tiny "particles" out of the soup.

The only "problem" seems to be keeping the plants happy. Since they don't talk, you have to second-guess their needs and constantly check their water, food and pH.

It's kind of like keeping a pet, only more fun; you don't have to worry about it getting away or biting anyone!

The "A" and "B" refers to which one contains the calcium. (Usually the "B") The other contains the Potassium, Magnesium, phosphates and sulfates. Combined, the calcium would combine with the phosphates (and sulfates) and precipitate as insoluble salts.
The trick is to get the nutes diluted quickly. Start off with ± 75% of the volume with plain water, then dissolve the Potassium, Magnesium, etc. (usually the "A") and make sure it's all dissolved. Then take the calcium (the "B") and pre-dissolve it a separate bucket, and once dissolved mix it with the rest.
And away you go.

freemangreens- I've been to your site a few times and I love it.
greystroke- YES! that's what I meant but poorly described.
NOW I think I understand the whole nute precipitation thing. So, as soon as both buckets are FULLY dissolved I can combine them. Thank you everyone!

OOPS, Made a mistook. It's actually calcium AND magnesium in the "B"-solution (not just calcium), cause magnesium phosphate also precipitates.

mesagrower wrote:
So, as soon as both buckets are FULLY dissolved . . .
Yep, but in the maximum amount of water as you can manage.

Okay, a few points I didn't see get made.

First, the A & B part nutrients (also called 2-parts, and there's 3 part nutrients as well) are only in liquid form. Dry nutrients don't have to be separated because the individual grains are already separate. Due to solubility or measureing issues it's often easier to use liquid nutrients, which means they have to be bottled at very high concentrations. Imagine if you bought your liquid nutes at even just double concentration. You have to buy one gallon of nutrients for every 2 gallons of reservoir.

So the liquid nutes have to be very, very strong. At those concentrations certain nutrients will react (as others have said here) and fall out of solution in the form of insoluble salts that can't be easily returned to a soluble form.

In fact, this reaction can be rather vigorous, possibly even violent in some cases.

So the multi-part thing is only for liquids, and isn't a problem when they're properly diluted. You add one part to the reservoir, mix it in, and then add the next part and you don't have the concentrations necessary to cause problems. They're only bottled separately because at the concentrations necessary to make shipping and storing feasible they full banquet of nutrients won't mix.

With dry nutrients you skip all that, but you have to get them to dissolve which can be a problem (especially with the cheaper stuff). Generally, the more soluble a nutrient salt is the more expensive it is.

Think of your multi-part nutrients like a binary epoxy. You've got two separate parts because once you mix them you have something that doesn't sit on a shelf nicely. In the case of epoxy, it's a glue that's going to harden whether you use it or not, so you only mix as much as you need when you need it and keep it stored in separate, inert parts. In the case of nutrients it's just too bulky to store at full strength so you concentrate it so it fits on a shelf. In doing that, you have to separate out the parts that won't stay mixed at those concentrations.