3. The darkroom

3.1 How do I build a darkroom?

There's an awful lot to say here, and it is all very dependent on what kind of space (big/small, permanent/nonpermanent) you have. Kodak has a lot of good, sound advice on darkroom building, and I'm aware of one links covering the topic:

• http://www.darkroomsource.com

3.2 Can I use tapwater for ...?

Generally speaking: yes you can. The short answer comes from David Manzi, I quote:

Could you use it from a tap?
Yes you could, you little sap!
Could you use it for a mix?
Sure you could, without a fix!
Can I use it for a wash?
Absolutely, let is slosh!
But what about photo-flo?
Ooo I'm sorry, that's a no.

The general consensus is that normal tapwater doesn't contain any chemicals in high enough concentrations to influence photographic processes. This is assuming we are talking about water from a water company - well water may very well be unsuitable for darkroom work. The only exception is the final rinse with wetting agent (Photo Flo), where hard water may still leave drying marks; here it makes sense to use distilled water, water from an air dehumidifier, or bottled water (if it is soft enough).

This is only a general consensus, people have been complaining about their tap water's fitness for darkroom work. If you feel uncertain, you might want to consult others in the area (minilabs), your water company, etcetera.

3.3 How do I store chemicals?

A discussion that is coming up over and over again is what kind of bottles are best used to store chemicals. The best stuff, but you already knew that, is dark brown glass bottles with stops made for keeping chemicals in and air out. Glass doesn't let air through and is easy to clean, and these are the two most important considerations (brown glass also doesn't let light in that could harm your chemicals). These bottles are also the most expensive ones, so you might want to use them only for chemicals that oxidize easily, like developer.

Plastics are permeable to air, and not as easy to clean (chemicals can and will be absorbed by plastic and it'll never get out). The cleaning part is solved mostly by only using any given container for a single type of solution. How much oxygen can get to your chemicals depends on the type of plastic and its thickness (the thicker, the better). The best solution is metalized plastic, then PETE, HDPE, LDPE, PP, PVC, PS and last and worst Teflon. Here's an overview of plastics names, the numbers that appear inside the "recycling triangle" on containers from these materials, and what they're often used for:

3.4 How do I remove water marks?

A recipe by Richard Knoppow, found in rec.photo.darkoom:

"Try the following. Soak the film for a few minutes in plain water, then treat it for a couple of minutes in stop bath. Swab the surface gently with cotton swabs. If there is anything left treat it with a wash aid like Kodak Hypo Clearing Agent for a minute or two and again try swabbing. This should remove any deposits left by the Photo-Flo. Then wash the film for five minutes and treat in a mixture of distilled water with about one ounce per quart of rubbing alcohol added (Mike Gudzinowicz correct this if wrong) and about half the amount of Photo-Flow recommended by Kodak. Hang it up to dry without further swabbing."

3.5 How do I get rid of my old chemicals?

This depends on your local circumstances. If you're connected to a sewage treatment plant, just down the drain with it. The stuff you produce day by day on the toilet puts more load on the system than the relatively small amounts of waste chemicals you collect in your darkroom. It's more hazardous, too, to collect and store large amounts of processed chemicals in order to bring them to a depot (if you have one in your area). If you're unsure whether you're allowed to do this (regulations may vary), contact the guys who process your water - I'm sure they'll be more than happy to give advice.

People have reported no problems dumping chemicals into their septic tank system, although some take the precaution to dump them together with large volumes of water, eg. when the washing machine pumps its water out. If you are not sure your septic tank will survive photochemicals, contact your dealer (at the very least, you've got somebody to sue :-)).

If you cannot or don't want to dump chemicals down the drain, an often-heard advise is to collect it in a large cannister which you leave open in order to have the water evaporate. You can then regularly collect the crystals from the cannister and get rid of them in whatever way you get rid of other dry chemical waste (which all depends on local regulations). Take precautions against spilling or leakage, like storing the cannister in a tray that can hold the volume of fluid in the cannister.

Note that all these rules apply to hobby darkrooms only. If you're a professional, you should contact your local environmental authority and talk to them; most places have strict rules about chemical storage and disposal for professionally-run darkrooms and photolabs.

3.6 What's the difference between the various enlarger types?

There are two main types of enlargers: diffusion and condensor enlargers. The difference is in the type of light that hits the film: a diffusion enlarger has a light mixing chamber and/or a diffuse translucent panel in order to shed an evenly distributed, diffuse light onto the negative. A condensor enlarger uses one or more lens elements in order to produce a colliminated light beam focused on the negative.

You cannot say that one type is better than the other - a lot of photographers have taken foot in one camp and defend their type of enlarger in an almost religous way, but you will be able to produce good prints with both.

There are some objective differences due to the nature of the light:

• The specular light from the condensor enlarger tends to enhance dust, etcetera, on the negative. You need to be more careful, but it's not a very big deal. A condensor enlarger also tends to show more grain in the print, but see the next point. On the other hand, the images are a bit sharper, which makes them especially popular for small formats like 35mm.
• The specular light also gives higher contrast. This is hard to explain in just a few words, but it's a well-known effect discovered by a Mr. Callier in the early days of this century: specular light gives higher density readings than diffuse light, and the ratio between these density readings is called the Callier Coefficient. I won't go into the details, but it means you need to shorten your development times in order to correct for this effect. Shorter development gives smaller grains and this offsets the higher grain from the previous point.
• Again due to the Callier effect, you will have a difference in contrast between contact prints and enlarged prints with a condensor enlarger: contact prints always show the diffuse densities in your negative, condensor enlarged prints show the higher specular densities. If you make a contact sheet, you will usually need a higher paper grade for this contact sheet in order to see the effect you'll get when enlarging the negatives. This is not a very big deal - you can match paper grades quite easily (it's normally one grade difference), and for good prints the grade indicated by a contact print is just a starting point, anyway (Ansel Adams used a very soft grade for his contact sheets in order to get maximal information, thus completely bypassing this problem).