Hi everyone,

thought I would ask this on the forum as it's something I've been experiencing for a longer time.

Almost every time I make a shot and smell it straight after the extraction it's very harsh, sort of mechanical, like burnt rubber/paper. I'm currently using a fresh batch of Los Luchadores from SQM (James Hoffmann/Anette Moldvaer), roasted on the 9th of March, but I believe it's pretty much the same with other coffees as well (older/fresher ones). Is it possible that it's due to the higher levels of CO2 in the beans, or am I doing something wrong here?

My TC/PID combo showed around 90*C during the last extraction and my pressure is set to 8.5bar (boiler set to 1bar). I'm currently overdosing a bit with this coffee (17g), but I get the same results with lower doses as well. I backflush regularly (once a week) with water and do a detergent backflush 1-2 times a month. I smelled the water straight from the group and when it's hot it smells a bit (but just a bit) like wet paper, although it wasn't entirely clean and it was done straight after an extraction. When cold it tastes like normal water with no additional smell. The machine is connected to a Brita water softener (the big one which looks like a CO2 tank) and that connects to my cold water line. We do have very hard water in the area, but it tastes pretty good and has almost no smell what-so-ever (a bit chlorine if smelled straight after pouring).

Regards,
dsc.

EDIT: I've just tasted the water from the group (a bit colder now) and it tastes a bit mouldy. Could it be due to the group disk not being cleaned for the last few weeks?

Ouch.

1 - I doubt a Brita is going to do what you need. Hard to know without testing the water, but given your description I think this is a problem. But I don't think this is directly causing your "bad smell" issue.

2 - On the other hand... "I backflush regularly (once a week) with water and do a detergent backflush 1-2 times a month" -- Holy Filthy Machine Batman!!! You don't have to be as anal as I am I guess (complete detergent clean daily etc) but that is NOT frequent enough cleaning. Period. This is at the very least going to dramatically compromise your espresso - and likely in the exact way you describe. Do you use a spouted portafilter or a naked one? When was the last time you removed your dispersion screen and cleaned the block?

3 - 90C? Really? Is that an accurate representation of your brew temp? If so, that's 194F which is VERY low for that coffee.

Hi Chris,

1. it's one of those bigger commercial ones:



I'm not sure how good it is, but will have to do for now. As I said the water in our area isn't bad, but rather hard. We are having a guy over tomorrow to install a general 'whole-house' kind of water softener. I'm curious of the impact on the taste.

2. I didn't want to backflush to often with detergent as I've heard it can remove the oils from inside various elements and cause more bad than good. Besides it doesn't look too bad in my opinion (the group was disassembled and cleaned a few weeks ago):







3. I've got a type T TC stuck just under the bell of the group (which is like and inch above the shower screen) and it's connected to a rather precise (cold junction compensation) and calibrated (boiling water/cold bath) PID controller. 90*C is low I agree, but as both me and Nicholas discovered Los Luchadores is more pleasant (at least for us) at lower temps.

Funny thing is the second shot I tried today from the machine didn't have that strange smell, it was lemon-like and quite sweet.

Regards,
dsc.

FWIW, I was enjoying Los Luchadores at what my machine reads as 198F (and a lower dose). I suspect, given the distance from the screen, that my probe reads slightly high, but I have not used a Scace to confirm this as of yet.

That said, I agree with Chris. Remember, it's not the degree of buildup, it's the degree of the rancidity of the buildup that screws you up on the group. If you're worried about keeping your parts oiled, just pull a blank shot immediately after backflushing. I'd recommend detergent backflushing once or twice a week at the least. Flushing with water regularly (backflushing or regular flushing w/brushing) will help prevent "gunk" buildup, but as I understand it the enemy of a good shot of espresso is more the baked, rancid oil than just the gunk.

dsc wrote:I didn't want to backflush to often with detergent as I've heard it can remove the oils from inside various elements and cause more bad than good.

This is one of the most persistent bits of misinformation in coffee.
If you clean with detergent as often as I do, you'll want to pull a "seasoning" shot or two before you pull shots to drink just to make sure there isn't taint - but you're not going to damage the machine or do anything bad by cleaning the machine more frequently.

As note above - it's not the volume of build-up but rather the age of it.
It's not about "clogging" the machine, but rather about contamination.

dsc wrote:90*C is low I agree, but as both me and Nicholas discovered Los Luchadores is more pleasant (at least for us) at lower temps.

At a true brew temp of 194F, that coffee would likely have very light coloured crema, a very light body, very little chocolate and no spice notes and would be dominated by a very astringent lemon taste. Is this what you're getting?

Without the described temp, my guess would be your machine is dirty PLUS you're at too high of a brew temp (from your description) but if you're really running 90C, then that option is out.

When I read burnt rubber/paper, the first thing I thought was robusto in the coffee blend, but bad water in, bad espresso out. I chemical backflush once a week and water flush every couple of days on my A3. Those little holes in the dispersion disk like to get buildup in them and start to produce extraction problems as well.

Hi guys,

thanks for all the responses.

Jim: I don't know if my water has silicates, is there a way to check it somehow? As I said I do a chemical backflush once a month and regularly backflush with water / brush and flush the group after (almost) each shot. The burrs on my Major are a few months old and ground a few kg's of coffee which is probably nothing for them.

Chris/Nicholas: so true about the oils, I've cleaned the group and the water doesn't taste stale anymore.

Dave: I agree about the little holes in the dispersion screen, I've had that problem before.

Ok so I will have to change my routine, do a detergent backflush 1-2 times a week and backflush with water everyday + the usual brush/flush thing I do already.

Regarding the Los Luchadores the display shows around 90*C (90-91*C) during the extraction, but if I go below it it tends to get brighter and lemon like. Normally each shot has nice thick medium brown crema (sort of like whipped cream/butter thick) which sadly dissappears quite quickly, body is quite low and I get some butterscotch on the tounge/nose, rather sweet notes with some lemon and if the distribution is right almost no bitterness. I can't guarantee the temperature is really 90*C, but I'll be able to check it soon when my two new PIDs arrive from Nicholas. I have a second type T thermocouple which I plan to mount under the shower screen to measure the difference between the screen and the place where the current TC is.

Regards,
dsc.

Very interesting about the temperature stuff. I could be wrong, but if I understand correctly, under most circumstances the water at the shower head is the coldest water in the system--that is, I don't know of any machines that measure water in the brew boiler/HX that tend to read lower than brew temperature. Typically they are up by a few degrees from actual. IIRC, the E61 TC typically reads very high early in the brew process, but drops to a very small offset late in the shot as the system converges to brew temp.

Correct me if I'm wrong, Tom, but you still don't have a brew pressure gauge, right? If you're brewing shots with weak body and poor crema, particularly if your pours are looking good, I think I would suspect a problem with too low/too high brew pressure. I know that low brew pressure diminishes body, but if you're getting good crema production that simply dissipates really fast, that could be off in the too high direction; I don't have experience with very high brew pressures to know. Hopefully Chris or Jim can clarify that point for me.

If your brew pressure is off, I understand that the behavior at whatever brew temperature may be somewhat different than expected.