Check roast date first. Ensure coffee has been stored correctly and rested a week or two from roasting. Ensure it has been roasted within the last month or two for best results.
If you want an intense shot pull lower ratios, less intense pull higher. Most equipment will struggle to achieve a high extraction at a 1:2 ratio especially with light or medium roasted coffee, so your starting ratio depends on your equipment, personal taste, and coffee used. Aim to produce a shot in 25-40 seconds and taste the result. Alter grind or ratio to adjust the flavour:
Too acidic or sour then try:
a. increase grind size
b. increase brew temperate
c. increase ratio
Too bitter then try:
a. decrease grind size
b. reduce brew temperature
c. decrease ratio
Too thin or gassy then try:
a. leave the beans to degas for longer
b. could be improprerly roasted or unsuitable for espresso, so try an immersion to see if the flavour improves.
Channelling or spurting then try:
a. Check your puck prep technique (WDT)
b. Decrease brew temperature
c. Check clearance at top of puck (five cent coin test and check there is not too much room)
d. Increase grind size or use a different grinder
e. Dry, warm/hot basket
f. Tamping technique.
g. You may not be able to see channelling and spurting, and a patchy appearance out of the bottom of the basket may not indicate either is actually happening through the puck, but channelling should be apparent in the taste if mouth feel is inconsistent, both sour and bitter, or unusually thin considering the dose and ratio used…..so if your shot tastes fine, and you only think you are getting channelling because you see a patchy extraction on a bottomless portafilter, you may not need to change anything at all.
Uneven pour (dark on one side, light on another) then try:
a. Check your tamping technique
b. Check the machine is level.
Sloppy watery puck then try:
a. Check basket size
b. Five cent test (See above)
c. Nothing, You aren’t making pucks, you’re making coffee. Do not make any changes if the shot is good unless you think for some reason it can get better.
d. Backflush to ensure release valves are clean.
Coffee tastes less flavoursome
a. Check the roast date (beans are going stale?)
b. Aim to increase extraction (grind finer, increase ratio, higher temperature, lower dose, higher flow rate etc).