Is it safe to microwave C-41 chemicals?

Bormental · Aug 8, 2020

I am preparing to develop my first batch of C-41 film at home. Two rolls at a time. I am going to use this kit and, between batches, I'll be storing it in amber glass bottles with airtight caps at 64-68F ambient temperature.

Last night I did a "test run" simply using water to see how well I can maintain the target temperature. Heating 1L bottle of water from 64F to 102F by submerging it in water bath takes a loo-o-o-o-o-o-oooong time! I'm thinking to speed it up by using a microwave. I did a quick test with water to determine the duration, just getting it to 80F+ before moving to a hot bath is a huge improvement.

Is this crazy? Will I ruin the C41 checmicals by microwaving?

Dusty Negative · Aug 8, 2020

Bormental said:
I am preparing to develop my first batch of C-41 film at home. Two rolls at a time. I am going to use this kit and, between batches, I'll be storing it in amber glass bottles with airtight caps at 64-68F ambient temperature.

Last night I did a "test run" simply using water to see how well I can maintain the target temperature. Heating 1L bottle of water from 64F to 102F by submerging it in water bath takes a loo-o-o-o-o-o-oooong time! I'm thinking to speed it up by using a microwave. I did a quick test with water to determine the duration, just getting it to 80F+ before moving to a hot bath is a huge improvement.

Is this crazy? Will I ruin the C41 checmicals by microwaving?

You'll most definitely get an answer from one (or more) of the amazing chemistry- and engineering-minded folks here on this forum. My gut tells me, "crazy," but let's wait and hear it from the pros. What *I* wanted to suggest is that you invest in a sous vide. They're relatively cheap and will heat and then keep your water at a fairly exact temperature. It's what I use, FWIW.

AgX · Aug 8, 2020

The only (theorethical) issue I can see is that you overheat partially the solution.

NB23 · Aug 9, 2020

Submerging a bottle in water should be quick if you stir, and if your bottle is NOT plastic.

glass or metal works quikly.

In the past I’ve microwaved D76 with no ill effects.

dourbalistar · Aug 9, 2020

Have you given any thought to trying a sous vide cooker? CineStill even makes their TCS-1000, an immersion circulator specifically for film processing.

koraks · Aug 9, 2020

I don't see why this wouldn't work, provided that the container/bottle used is microwave safe. Make sure to uncap the bottle so the solution can expand without pressure buildup in the vessel.
The problem with partial/local heating isn't much of an issue due to the thermodynamics of fluids; convection will spread the heat out fairly quickly.

Go ahead and give it a try; it'll work I'm sure.

Agulliver · Aug 9, 2020

I am not an expert but I do have some training in both chemistry and physics. I would have thought that it's safe, in that its not going to catch fire or give off toxic gas. You do need to ensure the cap is off the bottle. The main issue with a microwave is that some such devices don't heat evenly, you might well find that you still need to do a lot of stirring of your liquids to reach the desired, uniform temperature.

Last time I did colour (E6) I submerged my chemical bottles and film tank in the sink. I hear of people using baths, chiller boxes and recently sous-vide cooking heaters.

voceumana · Aug 9, 2020

Long time ago, when I wanted to raise the temperature of a solution, I used a hot water bath for the bottle of the chemicals, but made the bath hotter than the desired temperature, and it did not take very long. In my current house, my hot water tap temperature gets to nearly 130 degrees F after I flush the water from the pipe to the faucet.

Mackinaw · Aug 9, 2020

I have used a microwave to heat up C-41 chemicals. Works well.

Jim B.

Donald Qualls · Aug 9, 2020

Search Amazon and eBay for "sous vide" -- this is the same type device that Cinestill has relabeled as a circulation heater, but starting around $30. I've got one that cost $32 plus (very reasonable and fairly quick) shipping on eBay -- it sets in 1F (or 0.5C if you prefer) increments from 32F to 212F (makes it useful for Df96 and other warmed B&W processes, as well as C-41 and E-6), will heat a couple gallons of tempering bath from cold tap temperature (here, from a 300 foot well, about 60F) to 102F for C-41 in under an hour (while I'm doing other things, completely unattended), and will maintain temperature to, according to the instruction sheet, about 0.5F for up to 8 hours before the timer shuts it off (I haven't found a way to disable the timer yet, but I have no expectation of ever needing a longer tempering time). It also has an automatic level shutoff (to prevent burning up the heating element), and all immersed parts are either food-quality stainless or some rigid plastic.

IMO, this is almost as much of a photographic bargain as buying dry chemicals and mixing my own developer.

mshchem · Aug 9, 2020

I've used a microwave in the darkroom for decades. The only thing I can say is that you use only a few seconds, like 6 or 7 seconds for a pint of solution. Don't try to do it in a bottle as it will over heat the top of the bottle and melt it. The old school Kodak plastic graduates work nicely
I mostly use it to bump up the temperature a few degrees for black and white . For color work I use a water bath or Jobo. But if I want to heat C-41 from 68 to 90 in the microwave it saves time in the water bath.
Stir the solution, it will not be uniform in temperature in a microwave.

Mostly comes in handy to warm up deionized water for mixing powdered chemicals. I have a dedicated MW, not really a sound idea to use the RadarRange in the kitchen

Rafael Saffirio · Aug 9, 2020

I use the microwave all the time to heat C41 dev and blix to 40C, for 350 ml is like 60 seconds

Steve906 · Aug 15, 2020

Maybe microwave the chemicals in a water bath such as a large jug of water with the solution bottle placed in it to even out the heating a bit.

Is it safe to microwave C-41 chemicals?

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