The two principal types of printing paper are the resin-coated and fibre-based varieties. Resin-coated papers, correctly known as polyethylene or PE, are easier to handle because the paper is essentially encapsulated in plastic with the light-sensitive chemicals applied to the resin. This reduces chemical absorption and hence processing times, particularly at the washing stage. A typical resin-coated print needs about 4 minutes to fully wash in an archival washer, whereas a fibre-based print needs at least 30 minutes. Resin-coated papers can be dried in a simple rack and do not require glazing. They are available in a variety of finishes including gloss, lustre, matte and stipple, and can be purchased in a range of sizes from 4" x 5" up to 20" x 24".
Fibre-based papers are the older and more traditional type, and react much better to toning and other special effects. Indeed, speciality papers are generally of the fibre-based type. They have a paper core with a layer of barium oxide to carry the silver. Processing takes longer, more chemicals are wasted and equipment it is more expensive. However they produce significantly better results than their resin-coated counterparts, and have superior archival qualities.
Photographic paper is graded using a system which currently runs from 00 to 5. This provides a means of controlling the contrast of a print. The lowest contrast or softest prints are made at grade 00, and the highest contrast prints or hardest prints are made at grade 5. Normal photographic paper is classified as grade 2. Grade may be selected is selected to control the contrast of a negative, or to achieve a particular artistic interpretation. If a negative is very high contrast, then a soft paper is needed to allow the tonal range to be rendered. A negative having very low contrast requires a hard paper to extend the tonal distribution across the range of the paper.
Most modern photographic paper is classed as multi-grade, or variable contrast. This allows a photographer to change paper grades by using filters which are either inserted into a filter drawer or dialed into a colour head on the enlarger. Multi-grade filters can be used above or below an enlarger lens. The preferred location is above a lens because this eases dust problems.