Wayne Boatwright > wrote:

:Only if the recipe was designed for using a scale to measure liquids. I
:have never seen a recipe that specified a liquid measure in weight.
:Volumetric ounces do not equal ounces of mass.

Lots of (good) baking recipes do. I much prefer them that way. It's
much easier to put a container on the scale, hit tare, and add liquid
until it reads the correct mass than it is to pour it in a measuring cup
-- it saves having to clean that measure, it's faster (you don't have to
wait for the liquid to stop moving to read the scale, the way you do with
a measuring cup), and it saves bending over to read the measure. I
convert recipes to mass the first time I use one, if I think I'll try
it a second time, and it makes sense to do so.

:Using a measuring cup, the volume of all liquids will be precisely the
:same, ounce for ounce.

As long as you use the same measuring cup. They're remarkably
inaccurate. And lots of things you measure in them are hard to
measure accurately, because they've got an opaque meniscus.

:Using a scale, I do not understand how the logic of the scale
:differentiates between an ounce of water and an ounce of molasses. The
:weight of equal volumes would definitely be different.

There are scales that allow you to set the density of the fluid you're
measuring, and they'll display the weighed quantity in fl. oz. or
mililitres. (Lots of industrial packing is done by mass, even if the
quantity is listed as a fluid measure, or a count.) There are probably
some that have common kitchen fluids built in, but I've never looked.