I purge the grinder in between shots. If I had a decent shot at say, 17.8 grams of beans to between 5-10 sec. to first drip & grind is working fine enough, the next day I will, depending, on how many seconds to first drip either leave the grams of beans the same, add a little more or have fewer grams. I level in basket across with my finger gently. Sometimes I touch around the edges gently to "seal" any potential openings for channeling possibilities. Then I tamp (not as hard as I used to, maybe not necessary). What I seem to experience is a slow start to first drip many times---10-12 seconds, then it will flow normal, but then before 25 seconds it is flowing a little faster going more tan/blonde color (which equates to sour for me). I have no idea why this could be happening except that as the flow continue before the 25 seconds, a channel opens somewhere? Arghhhhh, thanks.

A bit old beans?

Never. I use beans typically 4 days post roast up until usually 19 days.

I've had a similar problem when my grind was too fine, perhaps go a bit coarser and dose more? Your description of the problem sounds like grind is too fine, so the first drip takes awhile until the water forces it way through a crack.

I've thought of maybe putting about 18.6g dosing in instead of 17.4g & instead of 3J on Vario, putting it down to 3K. I guess I risk choking it, but a lot of this is mathematical equations in my brain as I do this.

I have had this happen a couple of times with unique light roasts, I can only assume the first drop is on point because of the puck density then the quick flow happens as a result of the hardness of the beans not being resistant enough? I have not put a lot of research into it only I avoid the coffee that caused the issue.

Grind much coarser! Your first drip is late due to too fine grinds and you get early blonding due to channeling again because if the too fine grinds. Change the "but" in the title to an "and" this phenomenon is pretty typical, even though irritating if you never came across it.

The struggle is real....sigh. I can go ONE step down on the micro coarser & dose up & have a gusher. So if I am using 17.4 grams of beans to setting 3J & first drop is 9 seconds, and starts blonding at 20 seconds(faster flow also), coffee may be too fine a grind it sounds like as it may be trying to get through the too fine grounds and when it finally breaks through I have channeling. If on a Vario, I want to try & dose up and make the grind coarser....I'm wondering what I would shoot for. If it was 3J, 17.4g at 9 seconds to first drip & 20 sec. to shut off cuz too fast & fine, would I shoot for say, 3L, 18.4g. I'm just confused with how much coarser to make the grind and how much to dose up.
What I ended up doing was per the advice of going coarser & updosing, I went from 3J 17.4g, 9 sec to first drop---- to 3L all the way up to 18.4g, and first drop at 5 sec., but blonded even quicker, had to definitely shut it off at 20 sec & sour. This makes less and less sense. One could never say I'm not trying cuz I truly am.......
I guess there are no more answers anymore to my dilemma. sigh.

Please change only one variable at a time, otherwise you will never know how which change affected the outcome. This is actually more important advice then any specific change!

Hello:

coffeeOnTheBrain wrote: ... change only one variable at a time ...

+1
Quite so.
Settle on a dose weight and don't change it.

I suggest anywhere ≥ 15.0 g. and ≤ 15.5 g., adjusting the grind till you get first drops at ~ 5 sec., not more than that, it will probably channel.
Don't go further than that dose till you have nailed a proper double and can get ~ 60ml in ~25s, independently of blonding.

Once you have that cleared, check the temperature you are brewing at.
A doble styrofoam cup in lieu of the PF and a digital kitchen thermometer stuck through the side will suffice to get a reasonably decent value from an average of five readings taken 3 minutes apart.
In my experience, coldish brew water invite early blonding.

I recently had the same problem with a newly roasted batch, four days on.

I had not taken into account that (because reasons), I had dropped the roast before my usual southern Italian colour.
A ~1.0° C rise in brew temperature fixed the problem and I'm reasonably happy till my next batch.

Cheers,

CIV