Phosphate buffered formaldehyde is used in the first 2 stations of a closed processor. A white precipitate is forming in the processor tubing, and the tissue is more difficult to cut than usual. One of the first things to check to correct the problem is the:

• A. Percent alcohol used as the first dehydrant
• B. pH of formaldehyde
• C. Type of clearing agent
• D. Water quality

Answer: (A)

Dehydration quality dictates whether water is removed smoothly from tissue and how the fixative residues behave in the processor. When a white precipitate appears in the tubing and the tissue becomes harder to cut, the first dehydration step is a prime suspect because it sets the stage for all downstream steps. If the first ethanol is misprepared—either not the correct percent of alcohol, stale, or contaminated—it won’t remove water consistently. That mismatch can cause salts from the phosphate-buffered formaldehyde to precipitate as the solution chemistry shifts, leading to white deposits in the lines and improper dehydration of tissue. The result is tougher, more difficult-to-section tissue due to uneven dehydration and possible salt precipitates traveling through the processor.

So, checking and correcting the percent alcohol used at the first dehydrant is the right first move because it directly affects water removal, prevents precipitate formation, and improves subsequent infiltration and cutting quality. Water quality, pH of the fixative, and the choice of clearing agent all matter, but they are less likely to explain the immediate combination of tubing precipitates and harder-than-usual sections as seen here.