Sections crumble or tear

WHY?

• This happens when the tissue is extremely dry - usually as a result of over processing but it can also occur when tissue has been incompletely dehydrated. So it is important to find that happy medium between incomplete dehydration and too much dehydration. There must be some bound moisture remaining in the tissue for the section to remain whole.

• If the tissue not cleared properly the effect is similar to incomplete dehydration and in fact incomplete clearing of tissue is usually caused by too much free water remaining in the tissue.

• A blunt knife will cause sections to crumble, and if the Wax too soft sections can also disintegrate.

• If you are using the wrong melting point wax for the conditions sections can crumble. For instance if you are using a high melting point wax in a cold environment the wax can become almost brittle and crumble because of the hardness of the wax whilst if a low melting point wax is used in a warm climate the wax will be very soft.

• If wax has crystallised from slow cooling. This causes the formation of a large wax crystal so that the wax is less homogenous, then it has a tendency to disintegrate. Rapid cooling produces a tiny wax crystal and a more homogenous wax which holds together better.

• Wax contaminated with clearing agent or water will crumble especially when it is floated on to warm water. If there is clearing agent present in the tissue the difference in surface tension between the clearing agent and the water is sufficient to produce violent interactions between the two causing disruption of the section. If water is present in the tissue the tissue components will disintegrate because there is no wax holding the tissue components together.

• Paraffin wax denatured from excessive heating or reheating causes a breakdown of the wax molecule so that it loses its elasticity and ability to adhere to other molecules. The result is a breakdown in the wax which causes it to become very crumbly.