The Beseler 23CII is a classic enlarger. I bought mine new at least 20 years ago, and that makes it of recent vintage. It's black, whereas the older ones are blue or maybe gray. The older ones have a sliding filter drawer near the lens for a red filter (not a swing out bracket), but are otherwise similar.

The 23CII head can be aligned in relation to the baseboard in both directions. In the plane drawn vertically out from the column, the head tilts via a small adjustment screw at the bottom of the rails. In the plane parallel to the face of the column, the two attachment screws can be loosened and the bracket tilted slightly.

The lens stage pivots to allow correction of verticals by tilting the easel, then restoring the focus by tilting the lens. Many consider this a useless function, and I have to admit to rarely (never?) using it. Normal printing requires that the lens be exactly parallel to the negative and baseboard, so it would be unwise to disturb it after a careful alignment. I replaced the thumbscrew with a standard slotted screw to prevent exactly that.

There is no provision to align the lens stage in the other plane. This would be a serious problem except for the fact that most 23CIIs seem to be accurately machined and don't need much correction there.

The best alignment method requires two mirrors, one with a small hole drilled in it. Either first or second surface mirrors are fine. One mirror can be most any size, 4" X 5" or larger is good, and is placed on the baseboard. The other mirror must be at least 8-10 inches long and an inch or more wide. Using a small glass drill (Black & Decker is one brand), drill a viewing hole near one end. This mirror is inserted instead of the negative carrier, with the hole far enough outside the enlarger head that you can look through it. Looking through the hole, you should see a reflection of the hole in the mirror on the baseboard. Unless the alignment is perfect, you'll see a tail or trail of holes. Pointing a small lamp up at the hole helps immensely, as does some white tape to make an X across the hole, or a round white "holesaver" as used with notebook paper. The two mirrors (and the enlarger parts) are perfectly parallel when the trail of holes collapses into one. You can check the lens stage by holding the drilled mirror against the lip at the front of the lens. The technique is extremely sensitive, so don't become obsesses with constant adjustments. No enlarger will hold alignment better than this technique can detect. Baseboard flatness will also be a limiting factor in your measurements. If you have trouble with this technique, practice by looking through the drilled mirror while standing in front of the bathroom mirror. The good lighting and ability to tilt the drilled mirror by hand will quickly show you what to look for. This technique is also perfect for setting up your camera on a copy stand to get it parallel to the target.

There are several improvements that can be made to the 23CII. For smoother focusing, the two support rods can be replaced with ground stainless steel rods from any machine tool supply company. They have to be cut to the right length, the ends tapped, and a groove turned in the middle to match the originals. Easy if you have access to a small lathe, probably not worth the cost if you have to pay to have it done. The smooth finish will improve focusing accuracy and being stainless steel they will never corrode like the originals. The plastic focusing bushings will also last longer.

The 23CII uses a 75W bulb and probably heats the negative to the same degree as any other 75W enlarger. I found negative pop to be a serious problem, so ordered the Beseler #8042 heat absorbing glass. This fits just above the filter slot and cuts about 50% of the heat. I don't consider that exactly state of the art, but it's better than nothing. See my related article on Darkroom Measurements for specific temperature measurements.

The 23CII is also quite bright. I use an autotransformer to reduce the intensity a bit. Aim for ten second exposures at the optimum lens aperture. This will give you time to dodge and burn.

Negative pop is worse if the negative carriers don't meet perfectly. Using a flat surface as a reference, gently warp (I dare not use the word "bend") the carrier plates until they are flat and meet perfectly. No one likes the terrible truth that maximum sharpness requires a glass carrier. It really does.

There is an additional problem with Beseler carriers that I should mention, though I have no good fix for it. As part of the manufacturing process, it appears that the carriers were "Timesaved". This is a sanding process that smooths the surface and imparts a nice "grained" finish. The problem is that it also removes more metal near edges and holes. If you lay a straightedge across the area where the negative sits, and view the surface against a light, you may see a gap next to the frame. The result is that even with the carrier plates perfectly flat, the negative won't be held securely around the perimeter of the frame. I believe this contributes to the severe negative pop my enlarger suffers from. Note to Beseler- Timesave the surfaces before punching the hole!

My 23CII had a black area behind the bulb that projected on the negative as an annular ring. It was only visible in prints containing perfectly even gray skies, but once my eye tuned in to it, it became intolerable. The area behind the bulb should be painted flat white. It isn't a 100% cure, but is good enough for most purposes. The real cure is to order the "two step" lamp house for the 23CIII from Beseler. This uses a larger bulb and should be superior. Note that this problem cannot be seen or measured with an empty negative carrier. You must insert a medium density black and white negative for the problem to occur. The reason is that the annular ring pattern is projected and focused on the negative, but does not directly image on the baseboard.

The condenser pack can shift side to side slightly, enough to vignette a corner. find the best position and glue a small wooden rail where ever necessary to prevent the condenser from moving. Always put the condenser in the same way.

Finally, you can reduce vibration and settling time by putting a rubber foot in the center of the baseboard. Trim it so it just contacts the table and doesn't cause the enlarger to rock!