Lay a fresh sample sheet onto a firm backing board and imagine that the sheet has been split into three sections. Clean none of the first section, lightly brush the second, and clean the third with a bit more pressure. Make sure that the lighting is flat, and avoid direct shadows or glare; you want to be able to see particulate dust but not confuse foxing or shadowing with dirt. This practice will help you feel the pressure before bringing a brush or cleaning sponge to an actual artifact.
The purpose of surface cleaning is to remove loose debris without dislodging many fibers from the paper. It is not an attempt to brighten the color of the paper. After safe cleaning, there may still be yellowing, watermarks, dirt that cannot be removed, and staining; some types of these stains should not be addressed by novices. If the surface begins to feel shiny, scratchy, hairy, or patchy in color, it is already being over-cleaned.
Use a soft conservation brush to sweep dirt away from the center of the sheet toward an open edge. Use short strokes to maintain control over the brush instead of long, sweeping movements. Try to keep your other hand resting against the support board rather than touching the sheet itself. Do not brush over breaks, raised media, torn corners, or loose fragments, as even light brushing could lift a corner and cause additional damage.
Use a conservation cleaning sponge in a different way. Test the sponge on spare paper first, using a small piece and light, lifting strokes or dabbing. Rubbing repeatedly may grind dirt deeper into the sheet, create surface abrasion, or pull fibers from the surface. Examine the sponge frequently. An excessively dirty cleaning face can re-deposit dirt onto the sheet; using too much pressure can leave a cleaner spot in a sea of unchanged paper.
Examine the three sample areas through a magnifying glass and take photos from the same position. Focus on finding raised fibers, changes in surface texture, streaks, and variations in color instead of measuring how much dirt was removed. Record the tool, number of passes, direction of brushing, and pressure used in a cleaning log. This documentation makes a vague impression of “just right” into something that can be reviewed and changed.
Before treating an original document, search for signs of powdery ink, pencil, and coloring media, as well as mold-like substances, high brittleness, previous repairs, and moist stains. These factors may make dry surface cleaning hazardous. Control is not indicated by a large difference between pre- and post-cleaning appearance. Control is indicated by a flat sheet, an undisturbed surface, and a minimal amount of dirt removed without leaving a noticeable cleaning pattern.
