Technique to slow down ROR

Discuss roast levels and profiles for espresso, equipment for roasting coffee.

Postby Birdcollin » Mar 19, 2019, 4:09 pm

I currently roast using a Solid Drum Huky. Every now and then I end up roasting a Natural Processed high grown bean that wants to run away right before 1C. When I say "Run Away", I mean that the ROR will hold firm into crack and stops declining so I end up roasting these beans to a higher temp in a shorter time span. For example, a roast with this type of bean will have a nice declining ROR after dry up until about 10 degrees before crack then the ROR will level off and it seems that to get it to continue declining, I'd almost have to turn off the gas or turn the gas down extremely low which would then stall the roast. I'm sure some of you if not all has experienced this with certain lots. Do you have a technique you could share to help me gain control of the roast leading into crack?


Postby mkane » Mar 19, 2019, 4:26 pm

At first, I was making small adjustments 1 minute before 1C. Didn't work so well so no I'm playing with making huge adjustments @ 1 min.I'll leave it there for 30 seconds or so, sometimes longer, then increase gas to the origonal position. Seems to have it somewhat under control.


Postby Birdcollin » replying to mkane » Mar 19, 2019, 4:35 pm

On my machine, I'll usually enter crack at around 1kPa give or take. If you were using my Huky, would you lower the gas to say... .5kPa one minute before crack then just before crack happens turn up to 1kPa???


Postby mkane » Mar 19, 2019, 9:10 pm

I was just out giving a couple of batches a try using gas dip. It seems to help but I can't go back to my previous setting. Try going back 3/4th of the way, say around .75kPa. My machine responds to gas adjustments faster that air.


Postby pcofftenyo » Mar 21, 2019, 9:11 am

There's nothing wrong with turning the gas off before 1C if that's what it takes to avoid flat lining the ROR. Unless of course the cup is worse with the declining ROR.

My last heat cut is to low/off typically 20-25C before 1C starts which is 1-2 minutes. I am raising fan after this gently.

I have learned that I don't like to raise heat during 1C so I don't do that.

With a high natural I'm assuming you're max gas @ appx 1M in, before TP. When/where are your mid roast gas cuts?


Postby edpiep » Mar 21, 2019, 10:50 pm

Hi Jason,

I use a solid drum Huky as well but have no real experience with NP coffee in my roaster. There is a thread on this forum that talks about how to approach naturals (the example used was an African NP as well) and it seems to have yielded good results. That being said, I have similar questions as Tom and others about your gas cuts coming out of DE/earlier on in the roast. How soon do you start cutting gas and to what degree?

Recently I have been trying to quell a similar issue pre-FC with a washed Ethiopian and have noticed it does much better with more frequent gas cuts coming out of DE and less frequent gas cuts coming into FC. Having there be enough room gas-wise (say .5kPa) to back off either 45sec before FC or after (or both). That might be worth trying simply from the standpoint that the plateau pre-FC is likely caused by too much energy coming into FC. Mitigating it with more gas cuts early has helped make that transition into FC smoother in the example I shared. Take that with a grain of salt though as I said I am using a washed ETH not a Natty.


Postby Birdcollin » Mar 22, 2019, 3:56 pm

Around 300 F drop gas to 3kPa. DE (around 325 F) drop gas to 2kPa increase fan. Around 365 F drop gas to 1kPa. Around 385 F increase fan again. 1C normally is between 395-402 F. This is my standard approach. Obviously I will cup the roast and evaluate changes I need to make. I think I'm going to try and cut the gas completely at around 365 F on my next attempt for around 10-15 sec then turn it back on. I don't want to leave it off for too long risking losing too much momentum. Part of my problem is that I try to minimize adjustments throughout the roast so that I can replicate it later if I find a profile that's amazing however, some beans seem to need a lot more attention and finesse than others which would require more adjustments. Its funny, I feel like I know what the solutions are to the issues I'm experiencing but its so damn difficult to break away from the norm. I guess if I had all the time in the world combined with a never ending supply of beans I probably could figure it out through trial and error. But I don't, that's why I'm asking you guys.


Postby ALfromtheLAND » Mar 23, 2019, 6:43 am

I've noticed on my gas drum roaster that a fan increase at 385,even if it's small, flattens out the ROR curve for a period of time.
Maybe make a single air adjustment at 325 and start declining your gas in the same fashion. That could extend your roast and give you more control over your ROR around first crack with this bean


Postby Birdcollin » replying to ALfromtheLAND » Mar 23, 2019, 11:53 am

I've tried a couple roasts on other beans where I've only made the one air adjustment at dry and have noticed the aromatics are more pronounced. I always thought air increases early in the roast equaled an increase in convective heat while an increase later in the roast had a cooling affect. Once again, I'm still going off of what I've learned in books and on the internet. I need to trust my own experience and intuition a bit more.


Postby ALfromtheLAND » replying to Birdcollin » Mar 23, 2019, 12:55 pm

I agree, air adjustment will take away heat faster later in the roast but it will still go up before it drops.
My palette certainly needs training but, time over temp play is more noticeable in the cup than any air adjustments I've made.
Just my own experiences