American Photography Image Production Technology Professional Tutorial

Author: Christopher James (USA)
Publisher:
Publish Date: 2006-06-01
Features: Using sodium/potassium bisulfite to remove photo spots
If brownish spots appear in the highlights or edges of the photo, they can be removed using a 1% to 5% sodium/potassium bisulfite solution. The method can be an immersion process, spraying the solution onto the surface of the photo, or selectively brushing the affected areas. Potassium alum can also be used to clean highlights, but this chemical will shorten the photo's lifespan. Additionally, this cleaning process should be performed only after all colors have been fully transferred. The specific cleaning steps are as follows: Soak the photo in the sodium/potassium bisulfite solution for 1 to 2 minutes, then rinse in clean water for 10 minutes. It is important to control the percentage concentration of the sodium/potassium bisulfite solution, as their reaction is stronger than expected. Therefore, it is essential to test with a test strip first and adjust the solution concentration accordingly. You can apply the solution individually to the spots with a brush or immerse the entire photo in the solution. If you notice the emulsion becoming brittle on the surface, remove the photo, let it dry, and then perform the final rinse. If all spot removal methods fail, you can improve the process as described below to avoid repeating the same mistakes.
- First, check if there are any issues with the sizing and hardening process.
- Try a different brand of pigment, as the cadmium red pigment formulas vary greatly between manufacturers.
- Similarly, try a different type of gum arabic, as there are many varieties, and not all are compatible with the pigments you use.
- Soak the photo face down in water for a very long time. However, this method has drawbacks: prolonged soaking can damage the paper fibers and sizing.
- If the above methods do not work and you find the problem challenging, dissolve 10 ml to 30 ml of ammonia in 1 liter of hot water and soak the photo in it. However, the effects of this solution may not be what you intend, so closely monitor the photo's changes. Of course, how long to leave the photo in the solution depends entirely on your personal preference.
During the process, be cautious of the fumes generated by the chemical reaction.
- You can also reduce the exposure time and expose the emulsion immediately after it dries, or try a different paper, as different papers have varying cleaning effects.
- Try increasing the proportion of gum arabic in the emulsion formula, as excessive chromium salts can sometimes cause issues.
- If multiple cleaning attempts fail, you can try splashing warm or hot water on the photo to see if it works. This method may cause you to lose all details in the highlights, but for gum prints, the overall effect is often more important than details. Additionally, spraying warm water can help open blocked shadow areas on the photo.
- You can also try Ilford's Acid Hardener as a photo cleaning solution.
- Finally, if you are satisfied with the entire process, you can repeat it for verification. Alternatively, you can use the photo as a base for another project and continue with painting, brushing, or other creative techniques.