Hi Everyone,

I feel like I've exhausted all variables and for the life of me can't figure out why my shots keep channeling. Or I think it's channeling. After hitting the brew switch, I get a decent flow ~3 seconds later for about 5 seconds. It starts looking promising as the pump gets significantly quieter as pressure builds up. And then......instantly the pump gets louder (as if I was just flushing the head), espresso flow increases greatly, and goes blonde in color. Puck actually looks good, smooth, and knocks out perfectly intact.

For my setup I have a Salvatore Semi-Auto (E61 grouphead), 58mm C-Flat Reg Barber tamper, Mazzer Mini grinder. New burrs on the grinder. Tried varying grind and dose ad nauseum. WDT to distribute. Feel like I've read about every book and gotten nowhere. The double filter basket that came with the machine is more tapered than ones I normally see.

My guess is I'm losing integrity of the puck or the puck/portafilter interface once pressure gets built up in the portafilter. Probable channeling on the edge as the puck has no signs of channeling otherwise.

Anyone have any ideas, seen this before, or have words of encouragement? I have a naked portafilter on order and should get it soon, so I'm running a bit blind here.

Thanks!

Jim

Forgot to mention - the beans are about 4 days old from roast. Velton's Bonsai blend.

Have you tried grinding finer, to the point where coffee is dripping out of the portafilter? It sounds like your grind isn't fine enough if its gushing and blonding in 8 seconds.

If I go finer, pump just runs and nothing comes out. Should I try backing off to a lower dose at this point?

Thanks.

Have you checked that you are not over-dosing by first locking the ready portafilter in then removing it and checking for damage on the surface of the puck from the group? Is the Mini clumping at all? Do you weigh your dose? How old are the burrs in the grinder? Have you tried letting the coffee rest longer? Have you tried a different grinder? What is the airspeed velocity of an African Swallow?

African Swallows, not sure. European Swallows on the other hand......

I'll take a closer review of my dose tomorrow after I sleep on it a bit. Maybe I am overdosing (that sounded funny) and grinding too coarse. Never tried a different grinder. Burrs are about 3 hours old (seriously). It's not clumping and I had similar results from coffee over a month old. In fact, I can't remember a good shot in years, but I'm absolutely willing to say the issue is likely on the handle side of the portafilter.

Thanks.

I would also suggest weighing the dose as at the very least it will eliminate a variable. Also, do you have any idea how hard you are tamping and, most importantly, are you consistent with it?

With all but the very worst distribution and tamping technique, the most likely causes of non-edge channeling and accompanying spritzes are:

• Beans that out-gas significantly during the shot. Once the hot water and pressure hit, it's like shaking up a soda can, and the released gasses expand and break up the puck from inside.
• Thick pucks: the additional thickness of high-dose shots - even with not-overly-fresh coffee - increase the difficulty for the CO2 and other gasses to escape, and fissures are more likely to form inside the puck.
• Shot-end breakdown: if you watch the basket base using a bottomless portafilter, you'll see - especially near the end of the shot - a series of sudden light patches in the flow which appear and disappear just as quickly, indicating small channels that appear and heal themselves. This isn't quite the same as "blonding" but this inevitable erosion of the puck's integrity just as surely signals that it's about time to end the pull.
• Random acts of blindness: you'll never see exactly where, and you'll never sort out exactly why, but even the most careful technique doesn't ensure channel-less shots. Split happens.

So the most common systematic channeling in the heart of the puck will be the result of coffee that's just a little too fresh for the puck thickness. The higher your preferred dose, the more you need to rest the coffee so it behaves.

It's probably best if the extra rest time is provided with the coffee still in whole-bean state, but you are really anxious to pull a shot or two earlier, consider waiting a little between grinding and pulling the shot. Once you grind, the thinking (though I don't remember any exact science around the timing I'm afraid) runs that the aging process is dramatically accelerated with surplus CO2 escaping quickly from the ground coffee powder. Just as a diagnostic experiment, try grinding and then wait an hour before making the shot. If there's any truth to this notion, and if a relative surplus of gas was causing your channeling, you'll have confirmed the source of your problem.

And the advice I have often given in cases like this is to invite another, preferably more experienced Barista over for an afternoon, share some good beer, and have them bring another grinder. If they own a Scace Device, all the better!

if you need to mail the 1st class airline tickets to me, contact me off the list for the address..

Jim - take Randy's advice. (And if the beer's good enough, I'll bet even coach tickets will do the trick...)