Yup I use a triple beam balance to measure out my hops and minerals, it's super easy. I usually don't think to measure liquids by weight though, I think everything I do is by volume.
I actually use one of those 100 g x 0.01g jewlery scales that they sell on Ebay for cheap. I'm impressed how precise they are given their price.
Based on a PM that John sent me I ran an experiment tonight:
A 40 Brix solution was prepared from 8g of sugar and 12 g of water.
Using a graduated pipette I then mixed equal volumes of the 40 Brix solution and distilled water. This solution measured at 21.2 Brix with the refractometer.
Using a scale I then mixes equal weights of the 40 Brix solution and DI water. The resulting solution measured 19.6 Brix.
That seemed odd and I created a 20 Brix solution from 4g of sugar and 16g of water. This solution read 19.6 Brix on the refractometer. Good to know how precise my refractometer actually is. I have the cheap one that most brewing stores and Cynmar sell. The ATC is also not working as advertised and I keep calibrating it with DI water before each use.
My calculations expected 21.65 Brix for the equal volume dilution and 20.00 Brix for the equal weight dilution. If I assume an error of 0.4 Brix at the 20 Brix point the experimental results match up with the expectations.
To answer another one of John's questions this happens because the volume that the sugar occupies depends on its concentration. This is the reason why the sg to Brix/Plato conversion is not liner in the first place.
A.J. deLange has written an interesting piece about that: http://ajdel.wetnewf.org:81/Brewing_articles/Sugar_Gravity.pdf
But for those of you interested you may also do the math using the formula for Brix:
Brix = m_sugar / (m_sugar + m_water)
You'll notice that when you try to calculate the Brix of a equal weight dilution the resulting solution will have 1/2 of the initial Brix. But when you try an equal volume dilution you'll need to convert Brix to sg to get the volume of the solution to be diluted. And that's where the non-linearity comes into the equation.
Just now I noticed that the equal volume dilution is not truly exact when working with sg. The problem is that the combined volume is not twice the sample volume. This does result from the fact that the volume contribution of the sugar changes when its concentration changes.
Basically we can't write
sg_diluted = (sg_initial * V + V) / 2V
The dividend is the new weight of the solution and is correct. But the divisor is not 2V due to the change in the sugar's volume. I think I also see this in my spreadsheet. The resulting sg for an equal volume dilution of a 1080 solution is 1040.2 and not 1040. But this I really consider too small to matter for our purposes.
This should have deserved its own thread since we are far from the original topic. I also hope I didn't create too much confusion.