It generally dissolves any AH dyes if those are present in the emulsion. Sensitizer dyes as well. I don't think this does anything w.r.t. actual development.Could a pre-soak do something to the AHL (which then does something to development)?
A pre-rinse is not recommended as it can lead to uneven processing. -- ILFORD HP5 pdf
Another aspect of prewash is a notion that it either promotes or inhibits even development.
One might think, since the swollen/pre-soaked emulsion is a little 'insensitive' to the first splashes of developer that come in the tank, evenness of development might be promoted.
On the other hand, some manufacturers, like Ilford, recommend AGAINST it:
Well, Ilford are wrong!
Well, Ilford are wrong!
I use Paterson tanks, have for 50+ years. These are the older ones, with the small tops. I urge everyone, using any type of tank, to fill the tank completely, leaving just a little air space at the top. I fill the tank with water (same temp as developer, 68F) agitate, and let it sit for a few minutes. I then drain the tank and allow it to rest upside down on the table to drain thoroughly. I use a towel folded up on top of the table. After a minute or so of draining from the pre-wash, I pour the developer in, leaving only a small amount of air space at the top. I then place the cap on and invert the tank while rotating, then rap the tank firmly on the table (covered with a towel). Don't do it too hard or you'll break the plastic!I have no particular dog in this hunt. I've done it both with- and without prewash with no notable differences, except - as covered up thread - some slight decrease in contrast when prewashing.
Howsomewever ... could you care to share your basis/credentials/experimental data as the OP has to explain how you know better than Ilford? I am not much for argument from authority, so Ilford isn't automatically right, but you must have some reason for saying this.
I have no particular dog in this hunt. I've done it both with- and without prewash with no notable differences, except - as covered up thread - some slight decrease in contrast when prewashing.
Howsomewever ... could you care to share your basis/credentials/experimental data as the OP has to explain how you know better than Ilford? I am not much for argument from authority, so Ilford isn't automatically right, but you must have some reason for saying this.
I do stand by my original statement "...it [prewash or presoak] either promotes or inhibits even development"
Another aspect of prewash is a notion that it either promotes or inhibits even development.
One might think, since the swollen/pre-soaked emulsion is a little 'insensitive' to the first splashes of developer that come in the tank, evenness of development might be promoted.
On the other hand, some manufacturers, like Ilford, recommend AGAINST it:
I use Paterson tanks, have for 50+ years. These are the older ones, with the small tops. I urge everyone, using any type of tank, to fill the tank completely, leaving just a little air space at the top. I fill the tank with water (same temp as developer, 68F) agitate, and let it sit for a few minutes. I then drain the tank and allow it to rest upside down on the table to drain thoroughly. I use a towel folded up on top of the table. After a minute or so of draining from the pre-wash, I pour the developer in, leaving only a small amount of air space at the top. I then place the cap on and invert the tank while rotating, then rap the tank firmly on the table (covered with a towel). Don't do it too hard or you'll break the plastic!
I agitate in this manner for about 30 seconds continuously, then invert/twist twice at 1-minute intervals, rapping the tank firmly at the end of each cycle.
Before I started doing this, I would get air bells. Now, never.
It is my understanding that pre-wetting the film prevents air bells from forming by destroying the surface tension.
That's certainly your experience, but I don't think you can generalize from that.
I have both done prewashing and not done prewashing and have never had an air bell. I always tap after every agitation, but I am using Nikor tanks and reels.
This suggests that the variable here isn't likely the prewash (or not) but either our tapping techniques or the tank/reels themselves.
This sort of makes sense to me. In my explorations of long development times/log agitation times, I found that plastic reels (or any other film support with plastic ridged walls) tend to trap liquid and/or not flow cleanly. With low agitation, this expressed itself as bromide drag. It might also be the source of air bells, I dunno.
I do "tap" or "rap" pretty aggressively after every agitation, though, so as to dislodge any air trapped along the film surfaces, so that could also be why I've not seen the problem.
In any case, I am not convinced that prewashing prevents air bells, but I don't discount that's a possibility when using the Patterson system.
In any case, I am inclined to believe Ilford. They know a bit about film processing
BTW, we've been here before:
Is there any possible harm to pre-wash before developing?
I just developed first ever roll of Tmax and, of course, it came out with the typical pink... unless steps are taken to correct, like pre-wash, longer fix, longer rinse, I learn. I am familiar with pre-wash, as I have been working with Arista, and its sheds its green stuff that way. So...www.photrio.com
So what is Kodak's position on use of a pre-wash with their films, I can't see any reference to it in documentation that I have.
Yes, but if you are using a replenish system, your used developer goes back into your stock tank or jug. If no prewash is used, then your anti-halation junk and whatever else is in there goes back in that tank or jug. I just don't get excited as some folks here to see my developer turn pretty colors. Especially when it comes to Foma films.Prewashing tames that somewhat in my observation.
I don't worry about anti-halation dye removal because even if I don't prewash, I use either a running water stop bath or multiple water exchanges to stop development. Either one of them flush most all the dye away.
Yes, but if you are using a replenish system, your used developer goes back into your stock tank or jug. If no prewash is used, then your anti-halation junk and whatever else is in there goes back in that tank or jug. I just don't get excited as some folks here to see my developer turn pretty colors. Especially when it comes to Foma films.
Almost all the Kodak documentation is more oriented to commercial development lines than it is to hobbyists.
However the hobbyist oriented documentation that does exist suggests a method that almost no one I know uses:
"Smoothly lower the loaded film reel into the developer solution in the tank, and attach the top to the tank. Turn on the lights. Firmly tap the tank on the top of the work surface to dislodge air bubbles. Provide initial agitation for 5 seconds, and then repeat the 5-second agitation at 30-second intervals for the remainder of the development time. (See the table below for agitation techniques for different types of tanks.) Drain the tank."
You can't really use a pre-wash if you are lowering film into the top of the developer filled tank, rather than taking advantage of the features of tanks that are designed for "daylght" use.
Well, Ilford are wrong!
I wish to politely disagree.
I do a lot of tank development. The first contains developer, the last fixer. The middle one is a running water bath fed from the bottom of the tank and overflowing from the top. I routinely place film reels or hangers into the second tank first, to prewash, and then drop it into the developer tank. When complete, it goes back into tank #2, this time acting as a stop bath.
Like I said, almost no one does it like this
Surface tension is a property of a liquid. It cannot be destroyed.It is my understanding that pre-wetting the film prevents air bells from forming by destroying the surface tension.
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