# C-41 Process Glass or Plastic bottles?

Discussion in 'Color: Film, Paper, and Chemistry' started by Sirius Glass, Sep 30, 2007.

1. ### Sirius GlassSubscriber

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I have decided to do my own C-41 film processing. I will be using a steel tank in a large steel sink filled with water at 102 degrees F. I will mix the chemical just prior to processing the film. My question is should I use glass or plastic bottles to get the temperature of the chemical to stabilize faster?

Steve

2. ### tim_wallsSubscriber

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My only experience is that I use plastic bottles for E6 with no problem whatsoever.

I plugged some numbers into Fourier's Law however to try and work it out, purely out of curiosity. Bear in mind I last studied science about 15 years ago though .

According to the Intarweb, thermal conductivity of PVC is around 0.19 W/mK, glass 1.05 W/mK.

The thickness of the bottles will make a big difference. Running the numbers for a plastic bottle with walls half a millimetre thick, and a glass bottle with walls 3mm thick, you're looking at about the same. If the glass bottle were 2mm thick instead of 3, the glass would be about 50% faster. If it were 4mm thick though, it would be about 50% slower...

Or to put it another way; use whichever is most convenient, it doesn't make that much difference ;-)

3. ### tim_wallsSubscriber

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...Oh, and one other thing; that assumes both bottles present the same surface area.

A square bottle of say 10cm x 10cm has a 'circumference' if you can call it that of 4x10=40cm. A bottle of diameter 10cm (i.e. a round bottle which will fit into the same space as the square one) has a circumference of πD = 3.141 * 10 = 31.41cm.

The square bottle will therefore present a surface area (assuming it's a 'straight up and down' bottle) approximatly 1.3 times that of the round one. If you plug the numbers back into Fourier, that brings a square PVC bottle with .5mm thick walls back more or less into line with a round glass bottle with only 2mm thick walls.

One of those plastic accordion (squeezy) bottles is going to present a much larger surface area again, of course...

Err, like I said. Use whichever is most convenient

4. ### Nick ZentenaMember

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I use a mix of glass and plastic for C-41 and RA-4.

Bleach goes into plastic. It doesn't mind oxygen.

Developer goes into glass.

If you're using a water math the plastic bottles can be light enough to float!!#@\$#\$@.

Oh the question was about speed? If it warms up quicker it'll cool down quicker.

5. ### PHOTOTONEMember

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I have always used plastic bottles for all color chemistry with zero problems or issues. Kodak ships everything in plastic bottles now.

6. ### Dave MillerMember

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That's true, but it's got to be the right type of plastic!

7. ### PHOTOTONEMember

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Well, if you purchase bottles from a photo supplies vendor, they ARE the right type, however.....

For over 20 years I have used 1/2 gallon clorox bleach bottles for E-6 chemistry with excellent results. You can get these by prowling around the trash cans at laundromats. Just rinse them out well, with multiple fills of water.

8. ### Bob F.Member

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I note that Ilford ship their chemicals in HDPE. Most non-specialist plastic bottles such as fizzy pop and water bottles appear to be PET but they seem to work OK for most things - I've had ID11 for over a year in such bottles. The accordion bottles I have are not marked.

I don't think there is much between plastic and glass for heat transmission. They are both good insulators but are both quite thin in this use.

9. ### dslaterMember

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I would say plastic. I have both glass and plastic bottles, and I can tell you that when I am cleaning them, I use very hot water. When I fill a glass bottle, I have no problem holding it and dumping it. When I fill a plastic bottle, it rapidly (almost immediately) becomes uncomfortable to hold.

10. ### Sirius GlassSubscriber

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Thank you for yor responses. I will be going back to Freestyle Friday to pick up some more plastic bottles.

Steve

11. ### tim_wallsSubscriber

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That's an interesting point actually - in my original maths I used the thermal conductivity of PVC as a typical plastic.

HDPE apparently has a thermal conductivity of approximately 0.5 W/mK, compared to the figures I was using of 0.19 for PVC and 1.05 for glass.

Given that, and the thinner walls of an HDPE bottle compared to glass, I'd say an HDPE bottle will almost certainly conduct the heat as well if not better than a glass bottle. Which would concur with dslater's experience.

Oh, incidentally I don't do C41 but I do E6 - Kodak ship all the E6 chemistry in plastic bottles with the notable exception of colour developer part B, which comes in a brown glass bottle. I keep the mixed chemistry in plastic bottles though, and haven't seen any problems (although I tend to mix it and then use it pretty quickly.)