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Distilled thoughts from the Scott Rao lecture
i know a lot of you owners come straight here and don't follow the blog, but you may be interested in this post
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But what does it mean?
I have just bought his book on roasting... I expect that like with most books and me recently, i read the first couple of chapters, and then rediscover the book six months later at the bottom of a heap of bills or something of the kind.
A question arises about leveling the grounds in the basket. If I dose lower than the maximum rating of the basket (19g in a 22g VST) and once stirred one thump on the mat and the grounds are below the rim of the basket, no finger or knife would ever touch the grounds. It has bothered me a bit that I cannot get it perfect before the tamper enters into the equation and the nutation has helped once the tamper does get there, BUT, has anyone come up with a tool to level the grounds, distribute them, for the low doses?
Personally I think it's hilarious
In terms of what the refractometer is doing it is measuring the amount of refraction in the water when it shines a light through it, the refractive index of water being a constant, so the difference being attributable to the solubles from the coffee
Looking forward to seeing what a professional might have designed, thanks!
He said there may be an optimum for a particular machine, but certainly not across all machines
He also emphasised that an impression of the screen on the puck is ok if it occurs after the extraction only as the coffee swells up after the extraction
Whilst he didn't agree with it at all he said he knows of a guy in Australia who is adamant that the coffee should be hard up against the screen. I'm ashamed to admit that I don't subscribe to the huge clearance from the shower screen school of thought
I never worry about these things anyway.
As for the refractometer device, I understood that it measures %TDS, but I thought it did it through removal of the water (application of heat until only the dry residue remains), just shows how wrong one can be ...
It seems though that for purposes of accuracy, the same principle would remain, the water could be flavoured by its suspensions differently in one area to another, even though both samples might have a similar TDS.
When I play with the VSTlabs refractometer, I use it to note what the extraction % is, it is not a target in itself. Very fresh coffee extracts lower, and over-roasted coffee extracts higher without being wonderful. But when I love a certain shot and measure it, the % reading can suggest me to get a longer shot from the same beans next time to try a higher extraction, for instance.
I also got the Rao roasting book (all his books) and even though he seems not to know too much about fluid bed roasting, I took one hugely helpful suggestion of his to heart: a steep start of the roast temp and a declining Rate of Rise throughout the roast. It did noticeably improve my roasts.
As for the refractometer device, I understood that it measures %TDS, but I thought it did it through removal of the water (application of heat until only the dry residue remains), just shows how wrong one can be ...
It seems though that for purposes of accuracy, the same principle would remain, the water could be flavoured by its suspensions differently in one area to another, even though both samples might have a similar TDS.
Yes it does measure tds% Stephen
You could be correct on the rest of it too - it's 3am here and I'm off now, but I'll investigate
Ah no indeed not ;-)
Long before the VST refractometer was produced, Jim Schulman did lots of tests on extraction percentages and he then saved all puck cakes, dried them in an oven, numbered and weighed them all.
Nowadays the same analysis can be made much easier with the refractometer and filters.
That's why you don't use it to measure if a cup should be delicious. You can use it to check some facts about coffee you like or dislike. Just like a roast color meter tells you something, but not if the roast was perfect.
Consider this: if most super models are 180cm and 65kg (i don't know if they are), that does not mean that if someone knows a friend who is 65kg at 180cm, she could make money in modeling. But if you know a very photogenic person and she does not have that size and weight, she will not fit most dresses that need to be shown professionally.
Measurements can be very meaningful if used in a correct way.
What I have been doing is dosing the baskets high enough to barely touch, or a wee bit below that point, when the basket/PF is inserted and locked into the Group and then removed before pulling the Lever and then checking if that dose touched. It did not make sense to me to prep a basket, tamp, and then have all that effort ruined by interaction with the Shower Screen.
Where am I going wrong with that thought?
So far the biggest differences I have noticed are with the grinders and the flavors that they bring out in the cup.
@Reiss, are you still recommending 15.8g with your double basket?
If you have taught yourself that, you can eat your heart out experimenting, but if you get confused and disappointed in the results you can quickly return to great home base recipes.
Two baristas of a successful Amsterdam specialty place who are opening up their roastery and cafe soon, told me they frequently work with a recipe that they like very much even though the extraction % could just be 16.5% instead of the 'desirable' 20-24%
I could see how an updosed under extracted brew could be lovely and not cause any trouble.
I am interested in this myself, having just acquired a 3D printer that is now undergoing a lengthy calibration process. I'd love to know what people think such a tool would look like, or even better, see a model for it.
What I have been doing is dosing the baskets high enough to barely touch, or a wee bit below that point, when the basket/PF is inserted and locked into the Group and then removed before pulling the Lever and then checking if that dose touched. It did not make sense to me to prep a basket, tamp, and then have all that effort ruined by interaction with the Shower Screen.
Where am I going wrong with that thought?
So far the biggest differences I have noticed are with the grinders and the flavors that they bring out in the cup.
I'm brave enough to wager that you do get puck jump with a pump machine - guess when? when you turn the pump off, and i'll further bet that the jump is more pronounced than on a lever machine
i think the approach you detail above is correct stephen
yes i am paul, but I'm happy to be proved wrong - all i try and do on this forum is provide some guidelines that work for me so if people are struggling when they first connect their LONDINIUM up that they can get some decent shots and start building their confidence quickly
I am interested in this myself, having just acquired a 3D printer that is now undergoing a lengthy calibration process. I'd love to know what people think such a tool would look like, or even better, see a model for it.
its going to have a flat base, then a shoulder on each side where it comes up out of the basket and gets wider so it rests on the top rim of the basket so it runs level and then a semi circular top to give you some material to grasp it with
as you will have worked out, you will need different sizes for different sized baskets/preferred doses
I am interested in this myself, having just acquired a 3D printer that is now undergoing a lengthy calibration process. I'd love to know what people think such a tool would look like, or even better, see a model for it.
I think the uniform depth of the stirred grounds to the basket rim is the goal but different for every dose. That makes for something with a sliding stop collar that rests on the basket rim. I will try a sketch and get back to you.
you would use it by dropping it into the basket so the shoulders rest on the rim of the basket, and then rotating the card
i believe it would work
What I have been doing is dosing the baskets high enough to barely touch, or a wee bit below that point, when the basket/PF is inserted and locked into the Group and then removed before pulling the Lever and then checking if that dose touched. It did not make sense to me to prep a basket, tamp, and then have all that effort ruined by interaction with the Shower Screen.
Where am I going wrong with that thought?
So far the biggest differences I have noticed are with the grinders and the flavors that they bring out in the cup.
I'm brave enough to wager that you do get puck jump with a pump machine - guess when? when you turn the pump off, and i'll further bet that the jump is more pronounced than on a lever machine
i think the approach you detail above is correct stephen
When I saw the Vivaldi video that Frans Posted it stirred up the grounds a bit when the 3way valve actuated but not as bad as the gasp for air that the Lever causes. Frans played with this a lot, or at least as much as he could with that pretty weak clear PF I made for him.
That is basically what I had in mind.
I pondered this a year or so ago and did some work on it but lost interest with other bigger projects at hand. The 3D printer makes this possible.
OK, so what was causing the reverse/suction effect on the pump machine? Release of built up pressure in the Group?
The same thing happens when a pump shuts off in a pump feed espresso machine!
That's why they need to back flush them all the time! Every 40 minutes if you're someone like Rao!
The sudden closing of the pump causes the water in the line to pull back violently, not dissimilar to the recoil in a gun
In doing so it pulls a pile of coffee crud back through the screen