RE: LC-1 developer question
Fused silica. That's my guess. It's in submicron sized particles, (measured in nanometers!) and is used to thicken stuff like varnish and also to keep powders of mixed chemicals from separating out, such as the heavy stuff going to the bottom. It's inert and invisible when in solution. It may also keep crystals separated so they don't interact which is the possible answer here. I believe it is the magic stuff in "powder free" latex gloves. Talc is huge in comparison so I think they can call it powder free when used. --Dick -----Original Message----- From: Richard Knoppow [mailto:dickburk@ix.netcom.com] Sent: Sunday, March 30, 2008 12:29 AM To: alt-photo-process-l@usask.ca Subject: Re: LC-1 developer question -----Original Message----- >From: Ryuji Suzuki <rs@silvergrain.org> >Sent: Mar 29, 2008 10:39 PM >To: alt-photo-process-l@usask.ca >Subject: Re: LC-1 developer question > >There are a lot of things that don't really matter in real >life and if you look at old literature you'll find a lot of >them. > >Both Metol and sulfite can react with molecular oxygen >dissolved in water, but in reality, the rate of that oxidation >reaction is rather slow. Compounds that react with oxygen fast >are not very useful as a developer preservative. > >It doesn't really make much difference regardless of which >gets dissolved first, since a pinch of sulfite is not To clarify, I assume you mean in terms of the de-oxgenating the water since dissolving the sulfite first makes dissolving the Metol difficult. >instantly removing dissolved oxygen. If absolutely minimal >oxidation of Metol is required (such as in research >developers), it is probably more important to deaerate the >water and dissolve all ingredients as quickly as >possible. However, if deaeration is necessity for a particular >developer, I would have to say that the developer is poorly >formulated and not good enough for practice. > >If you dissolve Metol separately in an alkaline solution and >combine with high salt content, it may be easier to make all >the solids go into the solution. However, it is difficult to >say whether the dissolved state is stable. Even if the >concentration in the bulk solution exceeds the solubility >limit, the solution may be in the supersaturation >state. However, if there are some seed crystals, or some >debries, or even some rough surface on the container, the >crystals may grow on it fast (thus supersaturation decreases) >and only then you realize the problem. If the formula is well >made and well tested, none of these needs be worried on the >user side. > >-- >Ryuji Suzuki A related question: Do you have any idea of what Kodak does to make it possible to dissolve combined powder chemicals like D-76 and Dektol? Long ago some developers which are now a single powder came in two parts. -- Richard Knoppow dickburk@ix.netcom.com Los Angeles, CA, USA
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