I keep the tank in the water bath during all tempered steps. I fill it until the chemicals are about halfway up the funnel so that the film is submerged but there's still some room. With the rubber lid on it will float upright, which I like, and I take it out briefly for inversions every 30s. Better temperature control can be achieved by filling it all the way up so that the tank sinks, but my tanks are leaky at times so I avoid this.
Originally Posted by TheToadMen
If you're going to have the tank float you also have the option of using the little spindle to agitate it so that you don't even have to take the tank out. Entirely up to you.
The tetanal kit is three baths and uses blix, but as other people have pointed out you're better using separate bleach/fix solutions. Any colour film that's particularly important to me I have done at a professional lab, but for my fun snapshots these kits are more than enough (and are just as good if not better than your typical grocery store processing).
Regardless, have a go with it. There's so much lore around about how tricky C-41 can be, but it really isn't any more complicated than doing B&W. Pay attention to what you're doing and have fun---I had a great feeling of accomplishment when I saw my first roll come out.
I went the tub of water route at first, but I found I was always so nervous about the temperature being "just right" that it sort of spoiled the fun of the process. (I never liked fighting the off-temperature crossover effects.) So, I engineered a simple and cheap tempered water bath out of stuff you can get easily on eb*y and local stores. Here's a link to a post I made on APUG that describes this: http://www.apug.org/forums/forum40/1...velopment.html
While some will say this is overkill, I feel it really helps me relax and enjoy the process, not worrying about temperatures. Also, it gives me enough space so I can do processes like dip and dunk with lights out, not having to worry about monitoring temperatures.
That said, the tub of hot water did work fine for me until I built this. Color processing is sensitive to temperature, but it ain't brain surgery. Go for it!
I'm about to begin my own c-41 and E6 processing. Just ordered kits from Freestyle. So I'm reading this thread and others with interest. To regulate temp with my setup, I have a terrarium heater -- used to keep reptiles warm -- that is waterproof. It has no temperature control, just on/off. But I have built a dimmer switch into an outlet box and I will use it to regulate the heater's temp. The terrarium heater is actually a flat, flexible pad, about 10" square. I plan to set it in the bottom of the tub I'll be using. I have a selection of thermometers to choose from. One of them is bound to do a good enough job for monitoring temperature.
Ideally, I should use the mixed chems to exhaustion when I'm developing, but this won't always be the case. So to store my chems, I have several brown glass 500ml sample bottles. I was thinking I could pour the chemicals into these bottles and then remove any remaining air spaces by adding marbles to each jar, a la Aesop's "The Crow and the Pitcher." I'm hoping to maximize storage life this way.
I read somewhere that someone fills the bottles with buthan gass. I'm not a chemist, does anyone know if the buthan gass won't react with the developer, bleach, fix, etc.?
Originally Posted by cooltouch
Should work nicely, I'm guessing - besides flammable problems maybe, so don't smoke (ever!).
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read the msds from tetenal protectan. it's mainly buthane, propane and isobuthane.
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What power is the heater? If it doesn't have a built-in regulation mechanism, my guess is that it is going to be very low power (10W?) and will not be sufficient to heat your water up, though it might be enough to keep it about right or at least slow the fall of temperature... For comparison, a Jobo heater is about 300W.
Originally Posted by cooltouch
Read the C41 and E6 FAQs in my signature.
Originally Posted by cooltouch
The heater is 12 watts, which I was assuming was enough since it gets hot! Many reptiles like it really hot, which is why I was thinking it would be enough to maintain the temperature. I wasn't planning to use it to heat up the bath, just to maintain its temp. It has no built-in temp regulation. Just plug it into the wall. Which is why I mentioned using the dimmer switch.
Thanks for the heads-up on the FAQ. I wasn't aware of blix's inherent short shelf life. I guess the next time I order a set of chemicals, I'll think about one that has a separate bleach and fixer. If I can find one. The selection is getting mighty thin on the ground anymore these days.
Temperature and power are only loosely related, and by the thermal resistance between the item and its surrounds.
P = (T1 - T2) / R
- P is thermal power transferred between two items
- T1 and T2 are the temperatures of two items
- R is the thermal resistances (K/W) between the two items.
In your case, T2 is ambient (say 20C) and T1 is the bath, which you want to be 38C. If it's poorly insulated, expect maybe 0.5K/W thermal resistance, which means that you need at least 36W of heating to maintain the 18C temperature difference above ambient in the face of heat conducting away from the bath. If it's well-insulated (maybe 10K/W), you will need only 1.8W to maintain temperature, etc. So the power required depends entirely on how you build your bath.
Once you start agitating, your heat losses go way up due to evaporation from all the splashing about of warm water. Even though you can face about 150W of heat losses including evaporation, that still means a tiny temperature shift if you have enough water. 20L at 4.2J/(g.K) is 84kJ/K of thermal mass so with no heater and 150W of heat loss, that's a temperature drop of 0.5C in 5 minutes, which is totally acceptable for C41 processing. If I were you therefore, I would not bother with the heater (because 12W is totally futile in the face of evaporation losses) but just use plenty of water (20L) in an insulated tub to minimise conduction losses and provide lots of stability.
The heater pad feels "hot" (probably 50-60C) because when not attached to a large item like a tub of water, it has high thermal resistance to ambient. So its temperature goes way up until the thermal power balances out the electrical power.
^Thanks for that Polyglot.
Water has an impressively high heat capacity, so it takes quite a bit of energy to get up to temperature and it's hard to say if your little heater is up to the task. But I'll assume you're not starting with cold water, so it could very well work
Toad, being an aliphatic hydrocarbon, butane is fairly unreactive to most chemicals---but highly flammable! It should be fine for keeping oxygen out of your chemistry, as long as you're spraying it in a well ventilated area. Nitrogen, helium, and argon are also potential options, and possibly better options, if you have access to them.
After each use I pour my chemicals back to their stock bottles so they are replenished. If you do it this way the volume of your stock will be constant and you can buy bottles to fit the volumes snugly.
Thanks for the quick physics lesson, polyglot. Boy that took me back a few years. Like 33. After reading through it all, it almost makes me feel as if it were a miracle that, when I'd done E6 developing before just using a bathroom sink and ice cubes, things came out at all. But came out they did -- actually quite well, in fact. Yeah, I failed to mention that I was just planning to use a cheapo styrofoam cooler for the bath. They're cheap but they make for great insulators. Hey, if I don't have to use a heater, I won't. Just one fewer thing to worry about.