In general with air poppers, to slow down the roast, use FEWER beans. To make the roast go faster, use MORE beans. (Of course, if the popper is cutting out due to the bimetallic thermostat, it doesn't matter how much bean mass you have.) Brian On 5/14/07, Frank Awbrey wrote: <Snip>
Very true, Brian. Honestly, I remember reading an article about high altitude roasting, but I can't remember the contents. I think Diedrich Roasters had something on the subject. I mean, if water boils at a lower temperature then it makes sense to me that first crack would happen sooner, since you are basically converting moisture in the coffee to steam. Am i off base here? tom In general with air poppers, to slow down the roast, use FEWER beans. To make the roast go faster, use MORE beans. (Of course, if the popper is cutting out due to the bimetallic thermostat, it doesn't matter how much bean mass you have.) Brian On 5/14/07, Frank Awbrey <fsawbrey> wrote: Laurie, I am also a new (less than 30 roasts) roaster living at 7000 feet (approx.). I use an air popper, but not the poppery II. My very first roast burned/smoked and made charcoal of my beans in under 5 minutes (brand new, first time used popper). So, I think it can be done at this altitude. I then tried extending the roast times and actually got them up to 13-14 minutes long (not for espresso, tho). But I did not like the flavor and think that I was actually somehow stalling the roasts, causing it to, maybe bake the beans? So, I am back to quicker 5-6 minute roasts. Frank -- "Great coffee comes from tiny roasters" Sweet Maria's Home Coffee Roasting - Tom & Maria http://www.sweetmarias.com Thompson Owen george_at_sweetmarias.com Sweet Maria's Coffee - 1115 21st Street, Oakland, CA 94607 - USA phone/fax: 888 876 5917 - tom_at_sweetmarias.com
At first this wasn't making sense to me. I mean, higher altitude = thinner air = less heat transfer = slower roasting. Or so I was thinking. Usually electrical equipment has to be de-rated to a lower power rating at higher altitudes (usually ~86% @ 8000 ft, IIRC) because the thinner air doesn't take the heat away as well as thicker air. The same should apply, I would think, for trying to *heat* something with air. But Tom's point about the boiling point of water sounds more relevant, to me. Hmmmm. Gotta go look into this. On 5/14/07, Tom & Maria - Sweet Maria's Coffee wrote: <Snip> -- Larry J Never give a party if you will be the most interesting person there. - Mickey Friedman
If 1st crack earlier at high altitude do to moisture boiling point lower temp doesn't necessarily mean bean is "roasted" to typical 1st crack degree/stage, just that the moisture has caused the 1st crack effect. I'd expect 2nd crack to be more normal temp since not a function of water moisture IIRC, if you go that dark. Only speculating, no high altitude roasting experience. Guess we need a "roasting field trip" Gathering to Denver! Pacific Northwest Gathering Vhttp://home.comcast.net/~mckona/PNWGV.htmKona Konnaisseur miKe mcKoffee URL to Rosto mods, FrankenFormer, some recipes etc:http://mdmint.home.comcast.net/coffee/Rosto_mod.htmUltimately the quest for Koffee Nirvana is a solitary path. To know I must first not know. And in knowing know I know not. Each Personal enlightenment found exploring the many divergent foot steps of Those who have gone before. Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/ From: homeroast-admin [mailto:homeroast-admin] On Behalf Of Larry Johnson Sent: Monday, May 14, 2007 5:36 PM At first this wasn't making sense to me. I mean, higher altitude = thinner air = less heat transfer = slower roasting. Or so I was thinking. Usually electrical equipment has to be de-rated to a lower power rating at higher altitudes (usually ~86% @ 8000 ft, IIRC) because the thinner air doesn't take the heat away as well as thicker air. The same should apply, I would think, for trying to *heat* something with air. But Tom's point about the boiling point of water sounds more relevant, to me. Hmmmm. Gotta go look into this. On 5/14/07, Tom & Maria - Sweet Maria's Coffee wrote: Very true, Brian. Honestly, I remember reading an article about high altitude roasting, but I can't remember the contents. I think Diedrich Roasters had something on the subject. I mean, if water boils at a lower temperature then it makes sense to me that first crack would happen sooner, since you are basically converting moisture in the coffee to steam. Am i off base here? tom
But the roast could proceed more quickly to those temps because the moisture leaves sooner, nes pas? On 5/14/07, miKe mcKoffee wrote: <Snip> -- Larry J Never give a party if you will be the most interesting person there. - Mickey Friedman
On Monday 14 May 2007 17:57, miKe mcKoffee wrote: <Snip> Reducing moisture content at lower temperatures would mean the bean is drier and less dense sooner, but since the actual air is not quite so capable of transferring heat it seems to me that an *air* popper would take either much longer to get the internal bean temperature up to snuff, or simply not be capable of it at all, given how sensitive my popper is to seemingly minor variables. My instinct is that direct contact heat (as for example in a contact-based stovetop popper) would get you roasted beans nearly as fast as it would at sea level. The only way to know for sure without a field trip is to find two people with identical hardware and identical beans, I would say. For fan-based cooling, for example, thermal transfer depends to a significant extent on the density of the air involved.http://en.wikipedia.org/wiki/High_altitude_coffee_roastingThis wikipedia article is typically uninformative. It describes problems that high-altitude roasting could avoid, but not the equipment involved nor the physics. Plus the article insists that roasting should be as quick as possible and at the lowest temperature possible. "Red Rock Roasters" seem to think a longer roast is better at higher altitudes, directly contradicting the Wikipedia article, and "Taos Roasters" also takes upwards of 15 minutes for their dark roasts, and 10 minutes just to reach first crack. Now I'm just plain confused. :-) If all commercial roasters are convection-based then I suspect that the machines would have to work quite a bit harder at higher altitudes to come to temperature. It must just work out in the wash.
Tom, The boiling point may come into play. I personally think a big factor is the dry, thin air. I think it is more easily heated. If you think about going in the opposite direction, more and more moisture, until you were running water past the heating coil, the water would not get very hot in the short amount of time it was in contact with the heating coil. Whatever the explanation, I am convinced of the phenomenon. The very same popper that was so hot and fast in New Mexico had a hard time reaching second crack in the hot, muggy sea-level air of South Carolina. Brian On 5/14/07, Tom & Maria - Sweet Maria's Coffee wrote: <Snip>
There is less atmospheric pressure being exerted at the higher elevations. The difference between sea level and 8000' is approximately 3.8 psi. Water will boil at a lower temperature because there is less surface tension. The same atmospheric forces are acting on the coffee bean but have less effect on water in the bean because it is trapped by other forces than surface tension.
Can this be explained by the fact that water is being driven off at a lower temperature than at a lower elevation causing the exothermic process to begin at a lower temp? This would cause the beans to roast much quicker. Kit
On Tuesday 15 May 2007 10:25, Tom Ulmer wrote: <Snip> Since many roasters are air convection based roasters (including most popcorn poppers) I don't think the thinner air transfers heat from the elements to the beans as efficiently as at sea level. I found a lovely page describing the actual equations of thermal transfer for cooling fans here:http://www.comairrotron.com/high_altitude_cooling.shtmlThese equations are pretty clear about the (in)ability of thinner air to efficiently conduct heat. Conversely, the ability to transfer thermal energy by convection in the other direction should be similarly affected by air density. First off, cooking recipes don't need to have their temperatures modified but they never explain why. I think it's because the thermostat in an oven (for example) cuts out *when that temperature is reached* inside the oven. Therefore the oven will do more, or less, work as needed to hit the temperature you've set it to. Second, since the air is both thinner and less humid, it is not quite so efficient at convection-based thermal transfer between the source of heat and everything else, and therefore it seems to me it'd be easier to (for example) insulate homes at high altitudes. Perhaps that's why it's easier to keep stuff warm up there (insulators have an easier time of it) and that might provide a reason for the inability of an unmodified popper to work as effectively at higher altitudes. The boiling point of water I think would only come into play if the moisture content of the bean was an important heat conductor for the first stages of roasting prior to its inevitable exit-stage-left later on. Does this seem reasonable?
Marc, I'm not really sure what you said, but I'm ok with what you say as long as it is consistent with my observations: at 6500 feet my Poppery II roasted 1/2 cup of greens to second crack in 8 minutes, whereas at sea level the same popper had trouble bringing 2/3 cups of greens to second crack in 12 minutes, if at all. Similarly, a friend from Wisconsin brought his popper to Santa Fe and using the same procedures as in Wisconsin charred his roast into a smoking, oily mess. Brian On 5/16/07, Marc Tooley wrote: <Snip>
Do you use a variac? I"m wondering if the experience you found was due to elevation in total or in part, and how much due to voltage differences (you know those electrons get fiesty at higher elevations! j/k) -F On 5/16/07, Brian Kamnetz wrote: <Snip>
Floyd, I don't have a variac. Also, no difference attributable to extension cords, I don't think. I used a shorter 16 ga. extension cord in NM, and here in SC I used a longer 12 ga cord where I first lived, and plugged right into the outlet at my current place. (I have since switched over to HG/DB.) As I mentioned, a friend from Wisconsin was visiting his daughter (at 7000 feet) in Sante Fe and complained that he was burning his roasts. So he experienced the same phenomenon I observed at 6500 feet. He uses a totally unmodified popper, hasn't even removed the bimetallic thermostat. Brian On 5/16/07, Floyd Lozano wrote: <Snip>
On Wednesday 16 May 2007 13:44, Brian Kamnetz wrote: <Snip> Haha.. awesome. No, that's completely opposite to what I thought. :-) Ah, experimental data makes fools of us all at some point or another. How humid was the sea-level locale?
What i am wondering is if there is a voltage difference. Did you happen to measure the voltage at both places? A variac would have erased that as a variable, which could be a possible contributor to the difference. I'd expect a lower gauge wire to maintain voltage better (less resistance?) - dunno which you were using where. -F On 5/16/07, Marc Tooley wrote: <Snip>
Water has tremendous thermal capacity. Widely used for extinguishing fires. Heating elements dissipate electrically generated heat (watts) at a constant rate. When the nichrome element is glowing bright red to orange, it's actually hotter than Hell. If you hit it with a stream of water, you'll cool it down rapidly and the water will get no warmer than the cooled heating element. Hit it with a compressed air hose and you'll cool it rapidly and take away all the heat, again, at a low temperature. Downstream of the heating element, the massive airflow won't be hot and wouldn't roast coffee. Throttle the airflow somehow, and the element will get hotter, the passing air will get hotter as will the beans. Roastmeister is happy again. Water has a temperature-dependent vapor pressure. Heat the water, raise the vapor pressure. When the VP exceeds the ambient or atmospheric pressure, the water vaporizes or boils. At room temperature, water has vapor pressure. If you pump a partial vacuum, pretty soon the rt vapor pressure will exceed the ambient pressure in the partial vacuum, the water molecules will vaporize and become a gas called steam. It's invisible until it is cooled and condenses. There is no way to pay water molecules to violate the laws of physics. Put a damp bath towel in a vacuum chamber, and depending on the time period, temperature and pressure in the chamber, the damp towel will become bone dry. At the right temperature and pressure, you're done playing with water molecules- they turned into gas molecules and are invisible... Cheers -RayO, aka Opa! Equations don't cause things to happen, they just tell if a reaction can occur and how fast it goes- On 5/16/07, Marc Tooley wrote: <Snip> -- "When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty Wichita (ex- NYC Paramount) WurliTzer- 1976
Ray - I don't get it, but when I read your explanations, I get it a little. You should teach - or better, thanks for teaching in this classroom... VERY much appreciated... Brett On 5/17/07, raymanowen wrote: <Snip> -- Cheers, Bretthttp://homeroast.freeservers.com
I'm not really sure of the humidity range in either place, or of the voltage. Brian On 5/16/07, Marc Tooley wrote: <Snip>
Last summer I spent about 3 weeks in La Veta CO at 7013 Ft. I roasted HG/DB there and brewed drip pot and Aeropress there with no issues. I also did one demo roast at the gas plant located at about 8250 Ft and brewed drip pot there with no flavor issues. I understand the theory of why there may be concerns, but it just didn't seem to matter much in actual practice. Safe Journeys and Sweet Music Justin Marquez (CYPRESS, TX) On 5/17/07, raymanowen wrote: <Snip>
Justin, I think part of the question is how much excess capacity a particular roasting method has. Roasting with a Poppery II, I never had a problem reaching second crack at 6500 feet in northern New Mexico, but the same Poppery II was often not able to reach second crack at all here in SC, despite increasing the bean load from 1/2 cup to 2/3 or even 3/4 cup. Now that I have switched to HG/DB method with a 1740 watt heatgun, I roast here in SC with no problems. It also matters how the "problem" is defined. For me, moving from 6500 feet to sea level, the problem was that my popper/roaster would often not reach the first snaps of second crack. For my friend the northern Wisconsin flatlander bringing his popper to Sante Fe (7000 feet), the problem was that his popper/roaster burned the roasts, producing a racing roast that segued from first to second crack without a pause. Brian On 5/17/07, Justin Marquez wrote: <Snip>
<Snip> If there is a constant rate of dissipation, wouldn't that only matter if the density and humidity differential between sea-level air and high-altitude air was enough to exceed that threshold and cool the typical popper element faster than it could generate heat? Is sea-level air (being only one atmosphere) thick enough to act as that compressed air blower you describe for the average popper? <Snip> So restricting airflow (by for example putting your hand under the popper's intakes) would hasten the roast, assuming the denser sea-level air did in fact cool the elements faster than it could supply the heat.. that makes sense. That's why the popper is designed to vent air so well, and interfering with it tends to melt any nearby plastic. :-) (Like the butter cup.) <Snip> I was considering two things when I was thinking about this yesterday: 1. The phase change from liquid to gas is an endothermic reaction and therefore robs heat from the bean the moisture is evaporating from. If it boils off sooner, then the heat curve of the bean's innards sees a dip, sooner. But then how does this affect the rest of the curve? 2. While it is a liquid (and even in steam form) water is an excellent conductor of heat (which is partly why engines and turbines are typically water- or oil-cooled rather than air-cooled, the old VW bugs being a notable exception.) If it stays in the bean longer, wouldn't the water act to help the bean accept more heat, more rapidly? The steam exiting the bean would cause a dip later on, but wouldn't it reach that boiling point sooner? I was discounting the boiling point since, while different, I had thought it wouldn't make as much of a difference to the speed with which the bean was actually roasted (ignoring the speed of first and second crack.) <Snip>
I've been thinking about this issue for a while, and I thought of something I'd share. Higher humidity air does have a higher heat capacity at a given temperature, that's definite. But one thing I don't think has been addressed is the machine itself. You're using a popper. Most poppers, like similar small appliances, use a fairly cheap commutator/brush style of motor that's not speed controlled. It will either run at a known maximum speed under zero load (in a vacuum, in our case with the fan) or given a load it will run slower. The higher the load, the slower it will run, in general. When we're running this machine at higher altitudes, the barometric pressure is certainly lower, but I would argue that the fan motor runs at a slightly higher speed due to the decreased pressure on the intake side, thereby moving the same volume of air as it would move at higher barometric pressures. Of course this assumes the motor speed/cfm relationship is linear, which over this small change in pressure that's probably a good approximation. I think most of the issue comes from the reduced heat capacity of the air. Since the element's output is constant while it's on, the output air will have a higher temperature. You might argue that on the bean side the same thing holds true and there is less heat for the beans to remove per volumetric unit of air, but such a small amount of heat from the air is actually absorbed by the beans that I don't think that's an issue. I think the larger temperature gradient between the air in the chamber and the inside of the bean causes the bean to heat up more rapidly than it would at sea level, thereby speeding up the roast considerably. An interesting thing to do might be to alter the humidity of the air. Not sure how you'd do this though..maybe a spray/mist somewhere around the intake? It might be interesting even for those of us at lower altitudes as it might give us a way of controlling roast times other than cycling the power on the element (I've found that has a very rapid impact, so I don't do it). I suppose lower the element voltage would have the same effect, but maybe not. On Thu, 2007-05-17 at 12:29 -0400, Brian Kamnetz wrote: <Snip>