I am still pondering emulsion making, slowly amassing the gear and needed chemicals. What are the requirements for a magnetic stirrer, such as minimum volume, etc? Is a stirrer without a heater useless or is it possible to use with, say, a water bath and the emulsion in another beaker? If not, does a heaterless stirrer have any other photographic use?
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I have what was once a heaterless magnetic stirrer. I also had a salvaged 'bunn' commercial coffee pot warming stand. I extracted the heating element, and bolted to the underneath of the aluminum top plate of the stirrer, clear of where the motor spins the under platform magnet.
I also have a temperature controller, but have not yet integrated it into the heater control circuit. Right now I use the full on heater to keep developers hot while I wait for glycin, or crushed crystals of metol to dissolve..
The plan is some day to use this for emulsion making experiments, but in the mean time I work full time, as does my wife. She also studies part tiem, and then there are my 5 and 8 year old and thier activities. So perhaps the experiment may have to wait a decade or so.
I am still pondering emulsion making, slowly amassing the gear and needed chemicals. What are the requirements for a magnetic stirrer, such as minimum volume, etc? Is a stirrer without a heater useless or is it possible to use with, say, a water bath and the emulsion in another beaker? If not, does a heaterless stirrer have any other photographic use?
A waterbath that you have heated on another unit works just fine. The only disadvantage is that you will need to babysit the temperature a bit. Have some very hot water available to add to the waterbath as needed. The larger the volume, the longer it will hold its heat.
I make my waterbaths from glass storage bowls with tight plastic lids. (Pyrex brand is my favorite). You will want a bowl that is as high as about 1-2 cm shorter than the beaker you intend to use. Set the beaker on the center of the plastic lid and trace a line around the bottom. Then, cut the hole a bit smaller and cut little notches around the circumference. These 'fins' help hold the beaker down so that it doesn't float up in the waterbath before it's filled and heavy enough to stay down on its own. Punch a hole in the lid towards the outside edge to insert a thermometer.
A magnetic stirrer is very handy if you start to mix your own chemistry.
What would be nice is a container that has a drain/spigot so that you could drain the water when it gets too cool and then you could pour more hot/warm water in from the top.
Yes, as mentioned, you can stir a lot of hard to disolve chemicals into solution with a plate stirrer. But keep an eye out on the'bay for a used stirring hotplate. It even helps with those hard to dissolve chemicals as it heats the solution to help them dissolve in.
Kirk
PS - Mike, that looks like a lot of work. But I like your approach!
Jerevan, you asked about minimum volume - I'm not sure what you mean, as if you can put the beaker on the plate, you can stir it. But a plate with a 5x7 or so top is a good all-round size. They do make mini-stirrers that are say 4 inches square, but they are really not for the sizes of containers you would most likely want to use for general photo or emusion purposes. They make multi-stirring plates that can stir 6 beakers or so at a time, but that's definitely overkill for this use.
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Thanks for all the input. The cheapest stirrer I could find has a capacity for 1 litre. I am thinking of making emulsion to coat onto paper at first, for 5x7" negatives, but it is really a long way to go from where I am now. But at least I know a bit more about magnetic stirrers!
__________________ Photography reveals truths that reality obscures.
Interesting to me, too. Over the weekend I picked up a magnetic stirrer as part of a purchase of three boxes of photographic equipment, chemicals, paper, enlarger, etc. First estate sale I've ever been to and it was kind of weird going through other people's stuff, but, if anyone wants the stirrer, it's theirs. I'll probably never use it. It's an LKB Magnetic Stirrer Type 6901 A. Made in Sweden. It's set up for 115V. You pay for shipping. Weighs about a pound, pound and a half. If no one grabs it soon, I'll put it on the APUG Classifieds. If someone wants to give me money for it, all the money will go to APUG.
As for volumes, with gelatin present the viscosity makes it difficult to go above about 500 ml with good stirring. So, I use graded magnetic bars in 2" down for 500 ml down to 100 ml volumes.
Above 500 ml, I don't use magnetic stirring. Instead, I use a prop mixer, but I can add to the mixing at the bottom by using a prop mixer and a magnetic stirrer.
The convenient thing about magnetic stirrers is that they often come combined with a hotplate, so you get a 2 in one.
^^^WHS^^^
In my experience, mag stirrers are great for lower viscosity stuff, but a right royal PITA once it gets thick. I'd recommend a good triangular cross-section flea for stirring the thick stuff as its less likely to break away and go clickety clackety (PE knows exactly what I mean)
Prop stirrers are also good, but REAL men use a Silverson!!!!!!
My only other point to raise is that if you're using a stirrer hotplate, (you can get thermostatic controlled ones with a temperature probe), but otherwise don't heat to vigorously if you're using glass beakers. The bottoms tend to pop off if unevenly heated. This is where a water bath comes in handy.
For work I use stainless steel beakers, as I have to work in a glass free environment. These may be OK for a water bath, but might not be appropriate if you're handling silver salts and the like
Oh and a tip for those wanting to dissolve those hard to dissolve crystals: Get a ultrasonic bath off ebay (The sort used for cleaning jewellry) Once you've used one you won't go back. If you can handle the noise that is
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RING THE DOORBELL AND RUN,
HE HATES THAT.
Last edited by Aurum; 06-17-2008 at 07:37 PM.
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Requirements for magnetic stirrer 
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