Cal-Mag from Botanicare, an essential additive that brings Calcium and Magnesium, plus a trace of Iron. Here is the label:
Notice the ingredients, Calcium Nitrate and Magnesium Nitrate are the primary ingredients.
You may recall that Sweet is mainly Magnesium Sulfate, so let's just use Sweet to provide Magnesium to the plants and focus on Calcium. If you don't want to use Sweet, cross out the word Sweet and write Mag on the bottle.
Calcium Nitrate sells for about $3 a pound online, I got a 5 pound bag for $15 delivered.
The Cal-Mag labels shows us that it contains 2% Nitrogen and the total weight of the package is 366 grams, so 7.32g is N. The Calcium Nitrate is 15.5% N, so that works out to about 48g of Cal Nit in a jug of Cal-Mag. 48 grams worked out to about 10 Tablespoons. So put 10 TBSP of Cal Nit into a pan of water, heat while stirring until dissolved, cool, pour into a jug with cold water to fill and you have a jug of Cal-X, just Calcium. It also contains 2% Nitrogen, just like store bought Cal-Mag. The application rate should be the same as with the original, except you will have to use Sweet to get Magnesium. This gives you a bit more control over what you add by separating the Cal and Mag.
This seems too easy, what am I doing wrong? I made up a batch because I ran out of Cal-Mag and plan to use it with the next nute change.