Recommendations for stirrer / hot plate units?

[holmburgers]

Yeah, the prices are, *cough cough*, HIGH. I'm looking at the cheapest, junkiest looking one on eBay and even at $60 I don't really have the justification... yet.

I'm thinking that with small quantities (certainly less than 500mL, probably 100-200mL) of hot gelatin the viscosity won't be a huge problem, and yes digital would be nice, but again... $ $ $.

 

[holmburgers]

"•Microprocessor maintains consistent and repeatable temperature settings from 5°C (if ambient temperature is 0°C or lower) up to 550°C"

Excuse me?!?! That'll get you a rolling boil...

 

[Bruce Osgood]

Stick blender - now that's an interesting idea ...

I got away from the stick blender as it seemed to simply aerate the solution and add a nice frothing to the top. Not what I wanted.

 

[traveller]

Yeah, the prices are, *cough cough*, HIGH. I'm looking at the cheapest, junkiest looking one on eBay and even at $60 I don't really have the justification... yet.

I'm thinking that with small quantities (certainly less than 500mL, probably 100-200mL) of hot gelatin the viscosity won't be a huge problem, and yes digital would be nice, but again... $ $ $.

I know, the prices are high but I know nobody who pays them, especially Corning gets sold at much lower prices here.

What is the viscosity of the carbon glob? Gelatine in these quantity works, I just did give it a try with a magnetic stirrer capable to stir 10 l of water (that is a small stirrer).
How accurate do you need the temperature? With a little practice controlling within 3-5° is possible using a stirrer without digital control. Definitly better than using a kitchen stove and once you are in your temperature range you can use your time for better things than watching.

 

[holmburgers]

Between 110° and 120°F (43-48°C) is the ideal zone for carbon/gelatin "glop".

In addition to giving me some "free time", I am also looking for consistency of preparation to minimize any variables. The stove-top method has so far not been very scientific.

Cheers!

 

[greybeard]

"•Microprocessor maintains consistent and repeatable temperature settings from 5°C (if ambient temperature is 0°C or lower) up to 550°C"

Excuse me?!?! That'll get you a rolling boil...

Oops---please excuse the pedantry, but it is extremely common to see "temperature' confused with "heat". A kitchen match will give you a temperature much higher than 550C, but the amount of heat that it can transfer to a pot of water is almost negligible in the grand scheme of things. At the point where the rate of heat transfer into the spaghetti pot equals the rate of heat transfer away from it, the temperature will stop increasing.

As it happens, hotplates are not exceptionally good at heat transfer anyway, so if you really want good control of the gelatin you will want one with a separate temperature probe that goes into the solution, or, better, into a larger water bath that contains the smaller gelatin beaker.

 

[holmburgers]

As it happens, hotplates are not exceptionally good at heat transfer anyway, so if you really want good control of the gelatin you will want one with a separate temperature probe that goes into the solution, or, better, into a larger water bath that contains the smaller gelatin beaker.

But can a typical hot-plate/magnetic-stirrer keep a solution at 110-120°F? I imagine there would be a testing phase but once I obtained the correct knob position, it'd be better than my current setup. The water-bath variety seem to go for higher prices, though would be nice.

 

[greybeard]

The usual problem with stirring hotplates is that the top is larger than the container that you want to use, so there is a fairly small area of contact between the container and the plate (which is usually three points of actual contact and a thin air gap everywhere else). The container lose heat from the sides and top, so the plate has to be pretty hot to keep the container temperature up.

One solution to this is to put the small container in a water bath (such as an aluminum pan) that is about the size of the hotplate. To minimize evaporation, make an aluminum-foil cover for the water, or substitute sand for water. The idea is to have a large mass that won't change temperature quickly, and let the small container "go along for the ride". If you want to use a magnetic stirrer, the distance from the hotplate top and the magnet can't be too large, but an aluminum cake pan and glass beaker should be well within range.

If you didn't need the stirrer, a thrift-store crockpot with an incandescent light dimmer would make a great water bath. Manually holding 110-120F should be no problem at all, as long as your room temperature and air circulation don't vary too much.

Lessee....for a really cheap stirrer, maybe a thrift-store electric mixer, or a line-powered variable-speed electric drill? Cut away most of the blades on a mixer beater, bend the remaining tabs into propeller blades, and you could be all set in no time.

 

[holmburgers]

greybeard, I love the crockpot idea! Last night I was walking around Goodwill and the crockpots seemed to be "calling me"... haha!

But the dimmer is the key, as none of them have a variable thermostat. I might just go for that idea.

 

[greybeard]

Immersion-probe thermostats seem to bottom out at about $60--$75, but if I find a suitable one for much less than that I'll let you know. I'd like to have a similar setup, and I already have the $3 crockpot!

(There are probe thermostats sold for greenhouse propagation mats that would be perfect, but they don't go quite high enough in temperature.)

 

[holmburgers]

I'm using my crockpot right now, and between the low and warm setting, it does pretty good! Switch it every 20 minutes or so and it hovers right in the gelatin zone.

Should I just wire a rheostat/dimmer into a power cord for a variable crock pot?

 

[greybeard]

If you are handy (and competent) you can use a lighting dimmer; just be sure that you don't put more load on the dimmer (or wiring) than is proper and observe proper insulation and grounding.

There are also "electronic rheostats" sold specifically for controlling heaters, and a few "speed controls" for universal-wound electric motors that might have a high enough power rating. My Hamilton Beach thrift-store pot is only 160 watts on high, putting it well within the range of almost any of these devices.

If your crockpot has a two-wire cord (i.e., double-insulated) then a Lutron corded dimmer (300 W rated, about $10) should work fine. But don't try this with a "modern" crockpot having anything but a heater inside.


The Gelatin Zone: Wasn't that the title of a really cheesy horror movie?

 

[Ronald Moravec]

Heat your water in a microwave. Then put it on the stirrer and add thermometer. Add chemicals to make D76 or D72
( dektol). and watch the thermometer go up, not down.

This is called an exothermic reaction if I remember chemistry correctly, but 50 years is a long time to remember anything.
Actually remembering is not the problem, it is retrieving the information. I tend to forget the storage location like poor computer. We could do a whole discussion on this.

Anyway I did lust for heated one, but no longer.

 

[holmburgers]

Thanks greybeard, I'll go find a 70's crock-pot beauty at Goodwill soon and then head to the hardware store. The electronic rheostats, do they allow you to plug in an AC plug? That'd be convenient, but can wire up something if necessary.

 

[greybeard]

This

http://www.amazon.com/Lutron-TT-300H-WH-Electronics-Plug-Dimmer/dp/B0000BYEF6

should work just fine, and is available from places like Home Depot. Notice that it is a two-wire device, with no ground. If the crockpot is also two-wire, plug it in and you are good to go. However, it wouldn't hurt to plug the dimmer cord into a GFCI-protected outlet, because you don't know just how good the crockpot insulation really is.

Incidentally, it occurs to me that The Gelatin Zone probably isn't so much cheesy as tasteless. You know....Knox Unflavored?
Oh, never mind

 

[holmburgers]

Wow, that simplifies things a lot. Very cool.

The Gelatin Zone... is that like The Blob? Now that's a cheesy and tasetless movie!

 

[greybeard]

I think that The Blob was the large-format version of The Gelatin Zone (medium format...).

 

[holmburgers]

Update:

So, I went to goodwill yesterday to find a crockpot but instead found a Rival "Princess" fondue pot with a variable thermostat. Bingo!

Here's what it looks like -> Dead Link Removed

Cost me $5 and holds steady at 115°. However, the right temperature setting is well below the "1" setting and required a mark of paint so that I know where to set the knob. It's designed to get MUCH hotter, but hey, it works!

The cool thing is that the hole in the lid is the perfect size for a jelly jar of gelatin.

There are many kitchen appliances that would do the same thing; like electric coffee thermoses, etc., just gotta get creative.

 

[greybeard]

Congratulations. You are now a full-fledged member of the McGyver Memorial Institute.

If you are feeling really adventurous, you will now look inside the fondue pot to see if the thermostat has either a calibration adjustment or something mechanical that can be easily bent to place the 115 F point nearer the middle of the scale. It is sort of generally bad luck to operate near the low end of the scale, because of things like stick/slip friction and possible sensitivity to outside influences. Also, you could really cook your gelatin if you bumped the knob even a little bit. (Cooking your gelatin would be in this case equivalent to cooking your goose, only less tasty.)

 

[holmburgers]

Thanks Greybeard! If that's a real institute, I think you and Mike Wilde would be tenured professors.

Luckily the knob is quite sure, but I would love to get the right temperature up to the center of the scale. I'll see about it...

 

[fschifano]

Stick blender - now that's an interesting idea ...

That would mix in too much air. Not a good thing with developers especially.

 

[zencalculator]

According to me IKA 3368001 Topolino Magnetic Stirrer is the best option. Easy to use and super convenient. if you aren’t looking for anything bulky. It is the perfect bet for those who conduct small experiments and do not work with large quantities.