Does Rao's lighter airflow method apply to smaller roasters?

#1: Post by **texmachina** » May 21st, 2018, 12:52 am

I'm working on understanding airflow better when it comes to the Kaldi Fortis and cooler. After searching around, it seems many follow the low, medium, high relativity measurement using the lighter method shown by Mill City in their videos. However, I was wondering how relevant that method is for a roaster designed like the Huky or Fortis with a solid drum (similar design). Having never roasted in a commercial roaster before, are they more sealed up than the Huky/Fortis? Meaning, would airflow/negative pressure into the trier port be greater than a Huky where, for all intents and purposes the bottom is wide open.

The reason I ask is for me to get the flame to go into the trier port, I have to turn the Kaldi cooler fan up to 6-7 (out of a max 10), when most of what I've seen as far as instructions max it out at 1-3 during a roast.

Thanks in advance!

Edit: Corrected attribution in title

#2: Post by **aecletec** » May 21st, 2018, 3:28 am

The attribution as far as I know should be to Scott Rao, who popularised the method initially.
The best way to check is try a roast at different levels of airflow.
On my roaster which is vastly different to yours, I prefer much higher airflow.

#3: Post by **OldmatefromOZ** » May 21st, 2018, 6:52 am

I mentioned in the epic RAo baked coffee thread that in my experience on a Kaldi classic using the same cooler / chaff collector i've found the lighter test does not work.

FWIW without knowing your burner setup and how close you are sitting to the burner, how big the gaps are around your burner etc, 1.5 - 1.6 on the dial is my med to max setting. I use no airflow at the start first 1:30 and there is still some natural convection currents running through the system.
I them slowly turn the dial to around 1.4, I have 2 lines marked with pen for my tiny range.

This amount of air removes gases / smoke / chaff but pushes a normal cigarette lighter outwards at the trier hole when the burner is lit, more so at my max gas setting.

I've found using any higher airflow than mentioned just drags the exhaust temp down way too quick along with the delta ROR unless much higher gas settings are used which I found to make for dull roasty coffee.

May 21st, 2018, 12:31 pm

Thanks for the reply, Stephen.

I have ordered a new burner, hoping it'll show up this week. I feel like a lot of my issues stem from the inability to have fine control over my heat. I am also seeing the same thing with regards to falling ET when increasing the fan to anything over a 3. I feel like I am limited in ability to increase convective heat if raising airflow causes ET to crash. Again, I am thinking a lot of this is due to the burner I am using (LNG kitchen stove), and am curious to see what things look like with the new burner.

I am considering mounting a pressure phidget into the exhaust line between the roaster and chaff blower, just to have a more scientific way to measure airflow.

#5: Post by **OldmatefromOZ** » May 21st, 2018, 4:03 pm

texmachina wrote:Thanks for the reply, Stephen.

I have ordered a new burner, hoping it'll show up this w
I am considering mounting a pressure phidget into the exhaust line between the roaster and chaff blower, just to have a more scientific way to measure airflow.

No worries.

Yeah this sounds ilke a really good idea. I started thinking / looking for a viable way that i could measure airflow and it gave me a headache. It really is tricky finding the balance point where heat / air / time and a relatively smooth ROR come together to make delicious coffee and having reliable measurements of all will definitely help. Then the weather gets a bit cooler and you get a new coffee thats super dense and crashy....

May 21st, 2018, 4:26 pm

Ha so true! I am going to pursue the pressure gauge and will report back on how things pan out.

#7: Post by **Ross** » June 5th, 2018, 1:57 pm

This may not work on all roasters but on a drum roaster like the TJ-067 1k you can the run the roaster dry with artisan on and experiment with the fan to discover which fan settings are your hottest at at various gas settings used for roasting and how much cooling the fan settings above and below those settings provide. Those settings may not be 100% the same with a roast charge but will go a long way toward helping you make informed decisions on the fan.

#8: Post by **nickthorpie** » June 6th, 2018, 10:33 am

Make sure you read my last sentence.

I roast with a huky 500t. In roasting there are tradeoffs to every variable, and your job is to manipulate a variable to craft the flavour experience that you want.

In my experience:
Increase airflow -> increase acidity, decrease aromatic pungency, increased outer rate of browning, and a higher extraction yield

Decrease airflow -> decreased acidity, increased aromatic pungency, decreased outer rate of browning, lowered extraction yield.

For example, I carry a Rwandan that has unreal sweetness, but a sour edge. I want to roast light, but it just tastes like lemon juice.
One way I mitigate the acidity is by keeping airflow low unil first crack starts.

All of that is just to say that it is all relative. Rao's low flow method is good if those are flavours that compliment the coffee you're roasting.

If you're delivering a flavour that is complimented by the effects of higher/lower airflow, then use it as a tool. Let taste be your guide.

#9: Post by **nickthorpie** » June 6th, 2018, 10:44 am

Ross wrote:This may not work on all roasters but on a drum roaster like the TJ-067 1k you can the run the roaster dry with artisan on and experiment with the fan to discover which fan settings are your hottest at at various gas settings used for roasting and how much cooling the fan settings above and below those settings provide. Those settings may not be 100% the same with a roast charge but will go a long way toward helping you make informed decisions on the fan.

When I started roasting, I totally assumed that the fan would behave the same when it is empty as when it is full. When it is empty, increasing fan lowers the bean probe reading, whereas when it is full, increasing the fan increases the reading dramatically. What a confusing world