some question about "repeatability"


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Feb 1, 2006
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Hi guys,

I'm just a newbie in roasting and have some question about temp. in roasting.

I'm using local made roaster. It's provide bean probe and air probe.
I try to monitor both temp.

I've have heard that it's normal for first 3 batches we can not control much but after that it should repeat if we do everything the same.

my problem is even after those first 3 batches it's still can not control.
for example if the previous batch's 1st crack has ocured at 180c 10:00 minute. The batch after is crack at 11:00 176c since I've droped the beans at the same temp.(air temp)

I'm not sure if it's because of my understandard roaster.
I've never use other roaster.

would like to know what happend when you guys roast in Probat or other high standard roaster.

sorry for my poor english. :(
Are all your batches the same coffee?
Have you weighed it out exactly the same?
Have you dumped the coffee into the drum at exactly the same temperature?Temperature gauges can be notoriously innacurate on some roaasters.)
What kind of roaster do you have?
The main thing is understanding how your roaster roasts. this comes with roasting experience.

Just smell your coffee, listen for the cracks and wath your coffee sample probe and youll learn how to be consistant.

Keep roasting and learning :wink:
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  • #3
Thank you so much Chris for your encouragement.

Yes, I've done everything the same.
weight , temp. ,etc.

However, I wonder that maybe it's because my roaster has only 3 motors.
I have to wait until finish cooling before roast the next batch.

while it's cooling the temp. would droped, I have to wait for a while til it
reach the same temp.

I just wanna know how other roaster does , Probat ,Diedrich,Ambex.
what about their repeatability.

at the moment I'm interesting in TOPER roaster because of their attractive price. However, I'm not sure that it would solve my present problems.
Hang in there - you just need to find the zone and you'll be good.

My Ambex roasters are pretty consistent, once I get going. The first batch is different because I tend to heat up the roaster really hot to burn out any moisture in the stacks and prep the drum for roasting. I usually run a batch of "scrap" through on the first round...the stuff I give to neighbors and the lawyers across the street! Once the first batch is done, however, the 2nd batch on are usually very consistent, depending on batch size. Smaller batches go faster, so if I have small batches I do them last and adjust the gas flow.

It sounds like your roaster has some limitations. What size/brand is it? I watched a guy on tv sculpt a likeness of the Venus de Milo in ice using a pocket knife. At that point I decided I will try not to be critical of the instruments people use to roast coffee. A true artist will create the magic, regardless of the tools available. So please understand that my questions about your roaster are intended for information purposes and not to bash your decision to buy from a local source. PM me if you prefer.

As for finding the zone, Chris is can look at temps and ensure that you are dropping the beans at a consistent temperature. That might help. Is your gas regulated so that you can set the max temp? (again, it's why I ask the brand). Do you have an overridge switch to allow the roaster to exceed the max temp?

Stick with us - we'll help you figure this out!
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  • #5
thank you BeanGrinder

my roaster is local made,capacity 3kg.I would say that it has no brand.
It was constructed without knowlege about roasting.

so I think I'm using a pocket knife!

but I'm sure that I have had some terrific batches just like Venus de Milo.
however,I try to roast for business so to repeat it is very essential.

any way, with you and Chris help , I am keep trying and collect some more informations ,
using more my senses and will inform you later on.