Sweet Maria's Tip Sheet for The Caffé Rosto CR-120 Home Coffee Roaster

also on this page: Rosto Adjustments, Tips & Tricks


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Home roasting is fun and you will be amazed how easy it is. Pay attention to the process, especially toward the end of the roast. And be careful not to touch the hot roaster surfaces during the roast cycle.


In a nutshell, here is the roasting process you will be observing:


Adjustments to the Caffe Rosto

You have to realize that if you use the machine in an unorthodox way, one not specified in the official Caffe Rosto manual that comes with the roaster, you might be voiding your warranty! That said, the Caffe Rosto has been modified by many people, one reason it is so popular among advanced home roasters.

Chaff & the Screens:

You will notice that a decaf that has no chaff, and a dry-processed coffee like Harar that produces a lot of chaff will roast differently. This is because the later clogs up the air flow screens in the chaff collection chamber, while the decaf doesnt at all. Clog the exit air flow vent (where we put the tin foil in the image below) and you raise the temperature in the roast chamber, because more of the hot air is being redirected downward through the return air duct. But most chaffy coffees clog both, producing a mixed effect. Some people who use Rostos have chosen the remove the chaff basket that is *supposed* to catch chaff and keep the return air duct clean. They roast outside and simply blow most of the chaff out of the roaster - then stop the roaster just after 1st crack, clean the return air duct, and finish the roast process. Stopping the roaster like this is not ideal for the coffee or the roaster. More importantly, the Rosto is very hot an shouldnt be handled during the roast process, before the cooling cycle. Heed the warnings that come with the machine- you can get a real owie from the Rosto.

Simple modifications:

One easy way people have found to acheive darker roasts is to partly cover the outlet air vent (where hot air is blowing out of the Rosto) with tin foil or other heat-proof material. This redirects hot air back through the roaster. Now, the Rosto is already doing this ... it's part of the design. But additional blockage of the air grill will trap more heat in the roaster. A warning: by doing this you are exposing the motor and other internals to highger heat than the machine was designed for! You might fry the machine! A better way to attempt darker roasts is to use an outlet that has better voltage ... that means one on a circuit without a lot of other stuff running on it, and as close to your electric service panel as possible.

Below is a rosto with tin foil folded over and partly covering the exit air vent. Fully covering the vent would be dangerous! Partly covering it increases the amount of heat re-entering the roast chamber via the return air duct (the screen in the bottom of the chaff collection chamber as you look down on it. Messing with the 2 screens affects the roast a lot, which is why the amount of chaff produced by roasting, and where that chaff builds up during the roast has a large affect.

Here are the dramatic results of a Rosto with the outlet air vent partly blocked. The roast on the left is a setting of 11 and is a nice City+ roast. The roast on the right didn't even get to 11 before I had to advance to the cool cycle because it was billowing blue smoke! That roast is undrinkable!

This is a primitive way to affect the roast - and variable, based on the coffee and how much you block it. So you MUST keep a vigilant eye on the roaster if you do this!!! And you need to realize that if you fry the roaster by doing this it si your responsibility and Brightway will not replace it.


I would first try to block the exit air vent less than illustrated in this picture!

Adjusting the Cone:

A safer way to teak the roaster is to adjust the way the roast cone is positioned. The problem with the adjustment is it does not have a huge affect on the roast (in my experience), and you ened to take off the roast chamber to do it.


Remove the 3 screws inside the Rosto roast chamber.

Remove the roast chamber.

Lift the central hub of the roast chamber off the cone.

Here is the cone - it affects the roasters air flow.

Bending the flexible tabs on the cone inward allows more air to enter the roast chamber - this swirls the coffee more but can also let more heat escape the roaster (unless you have tweaked the exit airflow vent).

Place the cone back in the hub

Put it where it done was before...

And redo what you done undid before...
Now ... nobody who tweaks these machines has really explored the possibilities here - reshaping the cone? perforations in the hub? serious customization of the chaff collector? propane afterburner? digital roast color analysis? hmmm....

Other Advanced modifications:

Many people on our homeroast email list use the Caffe Rosto connected to a device called a Variac. With this they get total control over the roast. You can manually "profile" the roast with the Variac in a straightforward way - by adjusting the total volts going to the machine you can speed up/ slow down the air flow and turn up/ turn down the heating element. This will allow you to extend the roast times or spped them up as desired, and to achieve a darker roast if your voltage is a bit on the low side. The level of advanced modification and creativity people have shown is amazing, including PID (Programmable Input Device) controls to TRULY profile a roast, and they swear by the results. Join our Homeroast List for more information.

Check out Mike McGuiness' excellent web page as an example: http://mdmint.home.comcast.net/coffee/Rosto_mod.htm


This page is authored by Tom Owen and Sweet Maria's Coffee, Inc. and is not to be copied or reproduced without permission.

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