Magnetic mixer/hotplate for powder chemicals!!!

m1ckDELTA · Mar 21, 2016

This is probably old news to most, maybe.

I recently, as in yesterday, decided to try out a a magnetic mixer/hotplate. I find proper mixing of powder chemicals in order to keep oxygen contamination to a minimum and achieve 100% dissolution, tedious and time consuming. I usually let the mixture sit overnight in the gallon Datatainer to insure all the powder is completely dissolved. However, I want to know before I transfer the chemicals to the Datatainer that I have %100 dissolution.

Long story, short,...

Mixing film processing chemistry just got a whole lot more precise and, as a side benefit, easier for me; 100% dissolution of chemistry at the perfect temp with minimal oxygen contamination in short order. Set it, forget it, do some chores, come back, transfer to Datatainer.

Ken Nadvornick · Mar 22, 2016

Nice, isn't it? One additional advantage over manual mixing is when one is diluting solutions. It takes a LOT longer to fully homogenize dissimilar solutions than one may think.

For example, when the addition and dissolution of dry chemicals into a new solution is complete it's usually time to bring the maximum volume up to its final level by adding water. Do this with an automated stirrer, in a beaker with a light shining into it, up against a black background, and watch how long it really takes before you can no longer visually distinguish (by refraction) the two distinct solution types.

It's an eye-opener for anyone who regularly mixes the dilutions by hand with a half-dozen quick circles, then pours the still-differentiated solutions into multiple storage bottles for later use, assuming the mixing was complete.

Ken

Vaughn · Mar 22, 2016

I mixed hundreds of gallons of Kodak fixer by hand while a university darkroom volunteer. When I was hired to run the place, I made sure that we had a working magnetic stirrer! And we went to Kodak Rapid Fix in 5 gal cubetainers. I think I still hate Kodak Fixer...But I had a whole training routine I would give (and re-give) to new darkroom assistants on the use of the magnetic stirrer.

For personal use, I appreciate how I can stir pigments in to my gelatin without adding many bubbles. I use a tempered waterbath to hold three jars of pigmented gelatin at 110F for several hours and occasionally I transfer them to the magnetic stirrer to make sure the pigments are kept nicely dispersed. So far, I have not had a great need for a hot plate, but would seriously consider it if I needed to replace my stirrer.

m1ckDELTA · Mar 22, 2016

Ken Nadvornick said:
Nice, isn't it? One additional advantage over manual mixing is when one is diluting solutions. It takes a LOT longer to fully homogenize dissimilar solutions than one may think.

For example, when the addition and dissolution of dry chemicals into a new solution is complete it's usually time to bring the maximum volume up to its final level by adding water. Do this with an automated stirrer, in a beaker with a light shining into it, up against a black background, and watch how long it really takes before you can no longer visually distinguish (by refraction) the two distinct solution types.

It's an eye-opener for anyone who regularly mixes the dilutions by hand with a half-dozen quick circles, then pours the still-differentiated solutions into multiple storage bottles for later use, assuming the mixing was complete.

Ken

That is interesting. I didn't think about that aspect. Gonna check it out.

craigclu · Mar 22, 2016

Once owned and used, these seem invaluable and I am totally reliant on mine. One note: Resist the urge to use excessive rpm's as the cavitation can drive air/oxygen into the solution and have an effect on the activity life of the solution. On large, bulky projects like Xtol 5L mixing, I switch to a gallon glass thumb jug and gently roll it on its side until I am certain it is fully mixed. BTW, I then use it at adjusted dilutions from the mixed-to-gallon stock.

Alan9940 · Mar 22, 2016

I've thought about picking up one of these units. Anyone have any particular recommendations?

Thanks!

m1ckDELTA · Mar 22, 2016

craigclu said:
Once owned and used, these seem invaluable and I am totally reliant on mine. One note: Resist the urge to use excessive rpm's as the cavitation can drive air/oxygen into the solution and have an effect on the activity life of the solution. On large, bulky projects like Xtol 5L mixing, I switch to a gallon glass thumb jug and gently roll it on its side until I am certain it is fully mixed. BTW, I then use it at adjusted dilutions from the mixed-to-gallon stock.

I heard mention of "cavitation" while shopping for a unit. Does it really increase the surface's exposure to oxygen all that much more than without cavitating.

m1ckDELTA · Mar 22, 2016

Alan9940 said:
I've thought about picking up one of these units. Anyone have any particular recommendations?

Thanks!

I looked for the least expensive mixer/hotplate on Amazon and found what appears to be an unbranded Bipee for $90.

I've only used it once but it didn't have any immediate defects. When it first heated up there was the usual smell that is emited from new equipment that has a heating element.

m1ckDELTA · Mar 22, 2016

What kin

Vaughn said:
I mixed hundreds of gallons of Kodak fixer by hand while a university darkroom volunteer. When I was hired to run the place, I made sure that we had a working magnetic stirrer! And we went to Kodak Rapid Fix in 5 gal cubetainers. I think I still hate Kodak Fixer...But I had a whole training routine I would give (and re-give) to new darkroom assistants on the use of the magnetic stirrer.

For personal use, I appreciate how I can stir pigments in to my gelatin without adding many bubbles. I use a tempered waterbath to hold three jars of pigmented gelatin at 110F for several hours and occasionally I transfer them to the magnetic stirrer to make sure the pigments are kept nicely dispersed. So far, I have not had a great need for a hot plate, but would seriously consider it if I needed to replace my stirrer.

What kind of tempered water bath are you using?

Ken Nadvornick · Mar 22, 2016

Alan9940 said:
I've thought about picking up one of these units. Anyone have any particular recommendations?

Thanks!

Corning units are, for our purposes here, kind of the Rolls Royces of magnetic stirrers/hotplates. I have this unit as the full kit purchased new, but got a very good deal and didn't pay near the catalog price you see in the link. The kit came with the closed loop feedback external temperature controller, which I have never needed. But I have tested it with water and it works uncannily well.

This is a precision piece of lab equipment and is probably overkill for an enthusiast darkroom. But for the one-off deal, I would not have selected such a higher end model. However, automated stirrers in general are not overkill. Other brands and/or used units are plentiful and not overly expensive. Check the Ugly Auction Site.

Ken

Saganich · Mar 22, 2016

Couldn't live without mine. Thermolyne variable heat and colorsquid.

Vaughn · Mar 23, 2016

m1ckDELTA said:
What kind of tempered water bath are you using?

Jobo TBE2 -- image here (not my image): (there was a url link here which no longer exists)

I have sliced up the red bit of plastic to get three larger glass jars in it.

At the university darkroom we had Corning units. But students are rough on equipment and the last Corning magnetic stirrer we got started to act up after someone got it pretty wet...somehow. The speed control started to go south.

Properly sized (and shaped) stirring bars are a must, and some help with a stirring stick quickens things up.

ac12 · Mar 23, 2016

Oh you guys are BAD. Now I want another piece of gear for my darkroom. And the darkroom is still being built.

Ken Nadvornick · Mar 24, 2016

ac12 said:
Oh you guys are BAD. Now I want another piece of gear for my darkroom. And the darkroom is still being built.

Just so you know... it only gets worse over time.

Ken

m1ckDELTA · Mar 24, 2016

ac12 said:
Oh you guys are BAD. Now I want another piece of gear for my darkroom. And the darkroom is still being built.

A magnetic stirrer/hotplate really is a required piece of kit. I can't believe I didn't know about these. The whole set it and forget it aspect is key; chemicals mix themselves whilst mundane darkroom (or other) chores are not being put off. Proper lab glassware has been an eye opener for me as well. It is, after all, "chemistry" and when treated as such one develops and maintains a certain level of discipline.

m1ckDELTA · Mar 24, 2016

Vaughn said:
Jobo TBE2 -- image here (not my image): (there was a url link here which no longer exists)

I have sliced up the red bit of plastic to get three larger glass jars in it.

At the university darkroom we had Corning units. But students are rough on equipment and the last Corning magnetic stirrer we got started to act up after someone got it pretty wet...somehow. The speed control started to go south.

Properly sized (and shaped) stirring bars are a must, and some help with a stirring stick quickens things up.

I can't find a video or (free) manual online. How does it work? Is recirculated water continuously chilled or heated or does it require a constant flow of tap water?

Vaughn · Mar 24, 2016

Just a heating coil in the water hooked up to a thermostat which seems very consistant.. No pumps, no water flow. Holds a large volume of water and I try to put in water close to the temp I want so that it does not have to work too hard to bring that mass of water up to temperature.

m1ckDELTA · Mar 24, 2016

Vaughn said:
Just a heating coil in the water hooked up to a thermostat which seems very consistant.. No pumps, no water flow. Holds a large volume of water and I try to put in water close to the temp I want so that it does not have to work too hard to bring that mass of water up to temperature.

Thanks for that. I live in the desert so keeping chemicals below room temp is the goal for me. An electric Igloo cooler arrives today so I'm going to see if it will do the trick.

Vaughn · Mar 24, 2016

m1ckDELTA said:
Thanks for that. I live in the desert so keeping chemicals below room temp is the goal for me. An electric Igloo cooler arrives today so I'm going to see if it will do the trick.

I use to have something like that when I got knee surgery -- water got pumped thru the cooler and then around my knee.

ac12 · Mar 26, 2016

I need help from those of you familiar with a magnetic stirrer.
I dug one out of my pile of "stuff" and tried it with several bar stirrers. And they did not work/spin, the stir bar was just shaken or the whole bar was dragged around the beaker. However, a round one with a round flat magnet did work/spin.
On opening up the case, I found that the magnet on the motor was a flat donut shaped magnet, not a bar magnet. So a different magnetic field, and that is probably why my bar stirrers were not working. Anyone know where I can source a disc shaped stirrer that uses a flat disc magnet.

m1ckDELTA · Mar 26, 2016

ac12 said:
I need help from those of you familiar with a magnetic stirrer.
I dug one out of my pile of "stuff" and tried it with several bar stirrers. And they did not work/spin, the stir bar was just shaken or the whole bar was dragged around the beaker. However, a round one with a round flat magnet did work/spin.
On opening up the case, I found that the magnet on the motor was a flat donut shaped magnet, not a bar magnet. So a different magnetic field, and that is probably why my bar stirrers were not working. Anyone know where I can source a disc shaped stirrer that uses a flat disc magnet.

Pictures?

RalphLambrecht · Mar 27, 2016

m1ckDELTA said:
This is probably old news to most, maybe.

I recently, as in yesterday, decided to try out a a magnetic mixer/hotplate. I find proper mixing of powder chemicals in order to keep oxygen contamination to a minimum and achieve 100% dissolution, tedious and time consuming. I usually let the mixture sit overnight in the gallon Datatainer to insure all the powder is completely dissolved. However, I want to know before I transfer the chemicals to the Datatainer that I have %100 dissolution.

Long story, short,...

Mixing film processing chemistry just got a whole lot more precise and, as a side benefit, easier for me; 100% dissolution of chemistry at the perfect temp with minimal oxygen contamination in short order. Set it, forget it, do some chores, come back, transfer to Datatainer.

View attachment 153048

It's one of my favorite darkroom tools because ,I prepare all my processing solutions from bulk chemicals.

Magnetic mixer/hotplate for powder chemicals!!!

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