1. Will density.coffee help me with dialing in espresso?
Density.coffee will definitely help if you commit to this program.
Its works best if you keep a record of your grind settings at each density. With experience you can then fairly accurately predict what grind setting will be required for a given density. It’s linear so you only need a few points to generate the line.
The more you use it, the more you will find it gets it right pretty much first time 95% of the time. Dialing in almost becomes a thing of the past.
Because density.coffee varies all your tools of ratio, dose, yield, temp, time, grind, pressure relative to the density, it means there is less reliance on grind changes alone. You may find the range of grind settings that you commonly use reduces.
Density.coffee also gives you a really powerful tool for the challening 5%. Those difficult coffees where it’s stubbornly sour by using addition or bitter by using subtraction. You can do subtle shifts 0.1 to really big shifts 0.4.
That pulls all your levers of ratio, dose, yield, temp, time, grind, pressure in unison, making it really effective.
Density.coffee also gives you a view on what’s going on with your aging. When you should probably wait before trying, how long it’s good for, and guidance on storage.
A lot of coffee is being made with no regard to extraction changes required for different Roast Levels. Consequently most coffee is consumed more bitter or sour than it could be. Sugar and milk mask the problems, and people just get used to it. When you can find the sweet spot at every roast level, you can be surprised that you enjoy a wider spectrum of roast levels. If you think you don’t really like dark roasts or light roasts, maybe you just haven’t experienced a sweet one yet.
There are so many advantages to had from measuring density.
Measuring density helps you make the best you can from the coffee you have.
A good quality 100ml cylinder is still really cheap, there is little reason not to give it a go.
2. Where can I get a 100ml Cylinder?
Measuring Cylinder, 100ml – Class A, Tolerance: ±0.50ml – Borosilicate Glass, Blue Graduations – Round Base – Eisco Labs: Science Lab Cylinders: Amazon.com: Industrial & Scientific 
3. Density coffee assumes all coffee beans are a roughly average size, meaning blends and pretty common outliers pea berry, hard African beans or massive Pacamara wouldn’t necessarily fit the model or pack the same way.
Correct. Actually an earlier version of density.coffee included counting the number of beans in the 100mls, to factor in bean size variation. But it was found 95% of the readings resulted in marginal recipe change. Only 5% of the results delivered a significant benefit. The time taken to count the beans significantly degraded the user experience to the point of being completely off putting. In addition, with experience you can use your eyes, and expect that small beans will behave like a darker roast, so subtracting 0.20 from the measured density could improve results. Very large beans behave as if they are a lighter roast, so adding 0.2 could improve results.
4. I’m almost as against volume based measurements as James Hoffman
When it comes to measuring your espresso YEILD, volume is a terrible method compared to using weight.
However, when it comes to measuring DENSITY of a substance, it is its mass per unit volume. You need both tools, volume and weight.
You have to use the right tools for the job. Trying to use one tool alone for every job, would be like a Builder using a hammer to grind coffee.
5. I’m not sure this will get it right any faster than weighing out 18g eyeballing.
Good to hear you don’t advocate eyeballing 18g and are at least using scales.
Likewise, a 150 point density measurement is guaranteed to give you better results 99% of the time than your eyeballs for the Roast level.
6. Is measuring density really the magic bullet?
Before you were blind, now you can see.
Using a fixed 1:2 or 1:3 ratio recipe, fixed 93c temp, fixed dose, for every roast level of coffee, and relying on grind adjustments alone is worse than playing blind man’s bluff. It limits usable roast ranges to different methods.
For a very light roast on espresso that really requires beyond 1:4 ratio, a fixed recipe simply hasn’t used enough solvent water to get to the sugars. No amount of grinding finer will help, and the coffee will be sour. This results in preventing consumers using espresso method for light roasts, relegating many coffees to filter methods alone.
By only using espresso for mid to dark roasts espresso consumers miss out on many wonderful taste experiences.
For a very dark roast on espresso that really requires a 1:1 ratio and a much lower temperature, the fixed recipe has used way too much solvent water and heat. It is over extracted, no amount of grinding coarser will help and the coffee will be bitter. Typically dark roast fans use a lot of milk and sugar to cope with the bitterness.
Varying the recipe to one appropriate for the roast level as indicated by the density measurement means every roast level right across the spectrum of very light to very dark, can hit the sweet spot, neither sour or bitter, for all methods. You are no longer limited to what you can use on espresso. It’s liberating and wonderful.
Measuring density is not a silver bullet, but it is a tremendous tool that helps you understand what your coffee needs, and guides you on how to get the best out of it.