| The salton was certainly a bean basher wasn't it?! You can't beat my Sultan up anymore then I already have. It was never = very good, even when it was new. It was sold by QVC as a Cooks = Essential. I thought any test needed a variety from the best to the worst, I new = the Sultan flat burr would be at the bottom. Ron Kyle Anderson SC rnkyle |
| Today was my 60th birthday and one of the things I got was the time to do a few things I wanted to. One thing I did was make a mess of the living room by running two samples of coffee grounds through the set of sizing screens I put together. The first one was a sample from my Rocky set at notch nine, a little coarser than the six I use for espresso. The second one was from Ron Kyle's worn out flat burr Sulton. The way I conducted the screening was to take the sample, they were not the same size, and run them through each screen starting with the coarsest, which has 12 wires per inch, and is shown on the graph available at the URL below as "12". If all the sample passed through a screen that sample was scored a zero for that screen. If any of the sample was retained by the screen, it was measured by the following makeshift method. I poured the sample into a clear drinking straw and measured the height of the part of the sample caught by that screen in millimeters. I continued down through screen size 60. The last line was the dust that went through screen 60. My plan was to construct an bar graph of one straw for each of the screens and take a picture of it but that plan failed because the Rocky sample required more than one straw to hold the coffee caught by screen 42. I also discovered that the batteries were dead on my camera again so I just used one straw to measure with. The next time I am in a place where I can find some I will buy some measuring flasks that will allow me to measure volume in a standard measure rather than this makeshift millimeter of a clear drinking straw of an unknown diameter. Also, I was having to take care of my four year-old granddaughter while doing it and I think that in trying to do too many things at once I may have mixed up two of the measures from the Sulton. To a large degree this was a learning experience. For those with some statistical background, the kurtosis for the Rocky was 63 and the Sulton .03. Next, I would like for some of the others who got the sets of screens to get theirs put together and we could then go about replicating tests of different grinders. I would like to get a couple of samples from a Mazzer to see how it compares with the Rocky. By the way, Ron believed his Sulton was doing a bad job and hoped the data would demonstrate the need for a new grinder. I think it does. Anyway, you can see the results, and guess where the data may be mixed up, at: http://homepage.mac.com/jimgundlach/PhotoAlbum4.htmlThe page has two pictures, click on the right one to see the graph. Jim Gundlach Roasting over pecan wood fires in La Place, Alabama homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
| Terrific work! Looks like the technique is a success. Exact weights or volumes aren't really necessary, as long as each grind sample is measured consistently. Obviously, the Rocky performs better than a worn out Salton; but it looks like the same test could show any difference between grinders that are regarded as good to excellent, i.e. the Solis, Innova, Rocky and Mazer. Obviously, someone should send you one of each, gratis, for testing ;) Maybe I'm missing something, but wouldn't standard deviation rather than kurtosis be the proper single quantity measure of grinder quality (or rather lack of it). Jim Schulman On 15 Dec 2002 at 20:32, jim gundlach wrote: <Snip> homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
| Great job! I'm curious how the other grinders will perform, especially my MM. Feel free to mail me the screenings, I have a gram scale good to 0.1 gram. See the 'bell' curve is very informative. Dan |
| On Sunday, December 15, 2002, at 08:54 PM, Jim Schulman wrote: <Snip> You are right, the standard deviation is the traditional measure of variation and a more consistent grind would lead to a smaller standard deviation. Kurtosis is a measure of peakedness of a distribution which corresponds to the amount of variation but is not preferred because the values of kurtosis do not have the interpretive value that the standard deviation does. Rather it tells us how a distribution deviates from a normal distribution. Values greater than one are more peaked and thus have less variation than a normal distribution, and values less than one are flatter and have more variation than a normal distribution. However, when you have a variable where the levels are not continuous, as in this case where the screen is measured as number of wires per inch and the wires have different diameters, the numeric values of the standard deviation are not comparable when the means have different locations. In this case, the hole size generally gets smaller as number of wires get larger. However, the screen with 42 wires actually has larger holes than the screen with 40 wires. That is why they are reversed on the graph. Before I conduct the next analysis I will calculate the size of the holes and use those as the values for the screens. But, I have to go back to McMaster-Carr's catalog and get the size of the wires of a couple of the screens before I can calculate all of them. Once I get hole size instead of number of wires as the screen label I can compare the standard deviations. In general you are right, the standard deviation is the preferred measure and once I get the data in shape, I can use it. Jim Gundlach homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
| Thanks for the clarification. I didn't realize that the screen sizes aren't in a neat linear series. If the conventional ideas of grind quality are correct, a grinder that produces an uneven grind evenly spread of over three contiguous screen sizes is probably better than one that produces say 75% at one screen size, and 12.5% as boulders, and the other 12.5% as dust. So a measure that penalizes extremes even more than a standard deviation is probably required. A non-parametric version of Kurtosis may be the ticket. Jim Schulman On 15 Dec 2002 at 21:21, jim gundlach wrote: <Snip> homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
| Jim, very cool. I am surprised on the Rocky front since I had the notion from the Illy book that an espresso grind was a bimodal distribution where the fines were important for hydraulic control in the puck. I would have expected another, smaller peak at a small grain size. Hmm. The salton was certainly a bean basher wasn't it?! Ted *********** REPLY SEPARATOR *********** On 12/15/2002 at 8:32 PM jim gundlach wrote: <Snip> snip homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
| On Sunday, December 15, 2002, at 10:02 PM, Simpson wrote: <Snip> I'm sure it is possible, but right now I'm having difficulty imagining how you would make a grinder create a bimodal distribution. It may be the Illy blends the output of two grinders to produce their espresso. Guess I will have to get some to find out if it is bimodal. Jim Gundlach homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
| On 15 Dec 2002 at 20:32, jim gundlach wrote: <Snip> It's very interesting that the right hand tail on each is virtually identical. I wonder if that is an effect of the crushing action of the grinder. But wait...doesn't that indicate that they both have the same amount of coffee dust? -- Rick homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
| Jim, You are right, the hole size changes and sometimes not in the direction you expect. You can calculate the hole size if you have a micrometer or caliper to measure the wire diameter. Dan <Snip> homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
| <Snip> An optical comparator is the tool of choice for measuring hole diameters and web (wire) thickness (the wires wear with time when sifting material more abrasive than coffee). Inexpensive handheld ones are available from Edmund Scientific. At work we use a Nikon scope with projection onto ~ a 20'' diameter ground glass field, but that is a Fortune 500 solution. homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
| Both produced very little dust. It may be worth noting that both grinders use flat burrs. I should have noted that Ron sent two samples, a drip and an espresso grind. This is his espresso grind. When I built this set of screens I though the bigger screens were probably unnecessary. I don't think so now. Jim Gundlach On Sunday, December 15, 2002, at 11:37 PM, Rick Farris wrote: <Snip> homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
| R.N.Kyle wrote: <Snip> With pieces of the burr at the bottom it gives a whole new meaning to chunks ;-) <Snip> |
| HAPPY 60TH JIM jim gundlach wrote: <Snip> homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |