A home-made remjet removal bath

An at-home pre-bath for removing the remjet layer from Kodak Vision3 motion picture film.

Start with about 800 mL of distilled water.
Add about 156 g of washing soda (sodium carbonate decahydrate) and stir until dissolved.
Add about 19 g of baking soda (sodium bicarbonate) and stir until dissolved.
Dissolve the solids completely, then add enough distilled water to make 1 L.

The pre-bath will have a pH of about 10 (alkaline).  The solids are easy to dissolve.  Washing soda and baking soda are not dangerous.   If you don’t already have them at home, you can find washing soda in the laundry section of a supermarket and baking soda in the baking section.  Washing soda and baking soda are cheap enough that the pre-bath can be used once and thrown away.  You can filter and save the pre-bath for reuse if you're frugal.

To use, load the developing tank with film, then fill the tank with the pre-bath. Agitate vigorously and continuously for about 3 minutes.  Pour out the pre-bath.  Wash by filling the tank with tap water, agitating for about a minute, and dumping the water.  Repeat the washes until the water comes out clear and wash once more for good measure.  It will take several washes.  The pre-bath and wash water need to be close to the temperature of the developer you are going to use, usually 41 C (106 F).  After the remjet is removed you can develop the film following the instructions for your favorite C-41 or ECN-2 developing kit (like the FPP C-41 Home Development Kit or the FPP ECN-2 Home Developing Kit from the Film Photography Project Store).  After the final rinse I like to dunk the developed film in Photo-Flo diluted 1:200 with distilled water before hanging it up to dry.  While the film is hanging I use Kimwipes wetted with diluted Photo-Flo to wipe off the last of the remjet from the base side of the film.  Kimwipes won't scratch or leave lint.  You can get them from Amazon and others.

My recipe is based on the sodium carbonate pre-bath recipe from the Kodak publication Processing KODAK Motion Picture Films, Module 7, Process ECN-2 Specifications, which you can download from https://www.kodak.com/content/products-brochures/Film/Processing-KODAK-Motion-Picture-Films-Module-7.pdf.  Here is the Kodak sodium carbonate pre-bath recipe:

I replaced the anhydrous sodium carbonate with sodium carbonate decahydrate (washing soda).  The molar mass of the decahydrate form is 286 and the molar mass of the anhydrous form is 106, making the required ratio of decahydrate to anhydrous 286/106.  58 times 286 divided by 106 gives 156 as the weight of sodium carbonate decahydrate needed.  Because I used distilled water, I omitted the KODAK Anti-Calcium, No. 4, which is normally used to prevent calcium scum forming due to hard water.  I also omitted the Kodak Stabilizer Additive (TRIDECETH-4 according to information in the MSDS), which is a surfactant.  It probably helps to un-stick the remjet layer from the base side of the film.  The pre-bath seems to work well enough without it.  I kept the sodium bicarbonate (baking soda), which probably acts as a buffer.  You might be able to omit the baking soda and increase the washing soda to compensate.  I used a digital kitchen scale to measure weights.  I don’t think you need to be very precise.  Supermarket washing soda and baking soda aren't exactly chemically pure, anyway.  By the way, 156 grams of washing soda is about 2/3 cup and 19 grams of baking soda is about 1 tablespoon plus 1 teaspoon in kitchen measures.

Because solutions mixed from color developing kits have limited shelf lives, it is a good idea to save up your exposed color film and process several rolls at once in freshly mixed solutions.  Some remjet will remain in the developing tank when you are finished developing.  The tank and reels will need to be washed with soap and water.