Distilling maybe?

Jon

Very cool Nandina. Thanks!!

Living in wine country myself, this is also a topic I have researched. Concentrated vinegar solutions are obtained both through distillation (increases strength from around 5% to around 15%) and by freeze evaporation. But that will only generate a 30% solution of acetic acid at best. Anything stronger is obtained through non-organic (chemical) methods.

And yes, the 15-20% solutions are extremely caustic so exercise caution when using!

I want to use 20 % to kill weeds in my garden.
I am trying to figure out if it would be cheaper to
buy a Gallon of 20% vinegar or make the vinegar from powder.
Does any one know how much of powder vinegar is needed
for to make one gallon of 20% vinegar?

There's no such thing as powdered vinegar.

However you can use citric acid, available at hydroponics supply stores. Dissolve it in five times as much water by weight.

Don't apply it too close to crop plants.

Most vinegar powders are actually vinegar flavored powders with about 12% acetic acid and the rest being maltodextrin and starches. Some have citric acid added. All are weak.

Most acetic acids are made on an industrial scale by modifying alcohols. If it's dry enough, acetic acid will crystallize and can be ground to a powder, but that is an industrial chemical and it will co$t you.

"If it's dry enough, acetic acid will crystallize and can be ground to a powder, "

No ... pure (glacial) acetic acid is an oily, clear, incredibly pungent liquid. It doesn't dry out.

The "powdered acetic acids" for sale are maybe 10-12% with a lot of starches and anti-clumping ingredients.