Too Much Coffee

Hey guys. What would cause a roast to produce patchy, marbled, mottled, uneven colour coffee.

Too little coffee?
Too high initial temp burst?

Or is this just a trait of home roasting?

Could be the beans. Anytime I've roasted a Harrar for example it tends to be uneven.

It could also be your roaster applying the heat unevenly - what are you roasting on?

What did you use to roast Tris?

Gene cafe roasting gethumbwini...

My last but one roast was a little patchy as well (using a Gene Cafe). I have a voltage meter and I noticed the current was fluctuating throughout the roast, so I put it down to that. My last roast was fine (with a stable voltage).

Most of of our Gene roasts were even. We did notice that Geth was a little less uniform even in the Pinhalense, so it could be the bean type. Steve or Anette will prolly come and tell us why in a bit - harder beans I expect

I would guess - without knowing the profile - that it is a drying issue with that portion of the roast. Was first crack quite long and drawn out? It is a very dense coffee which makes even drying before maillards really kick in a bit trickier.

First crack always seems to be long and drawn out! Got it with me, will show you tomorrow.

I've roasted Geth quite often and it needs a longer roast than others. Ideally I would give it a ramp in temp right after 1C, but that isn't possible with my Gene. I have similar issues with Tierra Linda and also Kalosi.

I have to stretch it as far as I can and get there in the end...usually.

If roast is marbled etc, than I would presume that coffee is not yet ready, so under roasted.

Hmmm... pics?

How much did you put in the roaster. I have noticed with the Gene that if it is overloaded, then the roast can be patchy, insufficient airflow I guess. Highly chaffy coffees can cause this with a smaller load, as the chaff restricts the airflow.

I'll get a picture up soon.

I showed Jim Hoffmann and he concluded that being such a hard bean they needed a longer warmup to 1C and that in general roasting hard beans at home is pretty tough. The other problem with the gene cafe is that you can't load into a hot drum as you have to stop the cycle and remove it.

It was 125g of green.

Tristan wrote:The other problem with the gene cafe is that you can't load into a hot drum as you have to stop the cycle and remove it.

Well you can do an emergency stop, then using oven gloves remove the drum and load the beans. You can then start the cycle at over 100C

Tristan wrote:It was 125g of green. I showed Jim Hoffmann and he concluded that being such a hard bean they needed a longer warmup to 1C and that in general roasting hard beans at home is pretty tough.

But if you need a longer warmup then loading into a hot drum is surely going the wrong direction.

And I find it much easier and consitent to always roast at max capacity, or very near, I rarely roast less than 300g unless it is a chaffy coffee.

I have noticed this mottling with my current Colombian CoE.

The first few roast were pretty even and the beans were very even, however the past few have what you have described. Nothing changed really whether it was 150g or 200g. What has changed though is the temprature here as it has got a little colder, but I can't see that affecting it as the beans are stored in the basement garage which is pretty warm.

I have tried pre heat with these and thinking about it, that made a difference. Damn, why didn't I see that

Ah well...