Microtomy problems do not disappear with experience, but experience does allow the microtomist to identify and troubleshoot the problems quickly. Below is a summary of the most common problems that can be identified at the microtome. Many microtomy problems have several sources, so it is best to address them one at a time until the problem is resolved.
Ribbon will not form Sections curl, skip, or stick to top of block; ribbon separates easily | - Paraffin too hard; needs to be stickier
- Room/block too cold/hot
- Sections too thick
- Cannot seem to anchor the ribbon
- Angle of knife clearance is too small
- Blade may be caked and dirty
- Something in microtome not clamped down securely
| - Choose paraffin with lower melting point
- Adjust room temperature
- Decrease microns
- Dull blade slightly; introduce nick to one edge of blade
- Increase clearance to angle between 3-8 degrees
- Replace with clean blade
- Tighten all clamps
|
Crooked ribbons Straight ribbons difficult to form | | - Adjust the block holder to make the block edges parallel to knife
- Block holder must be aligned so that top and bottom of block are parallel to blade and sides of block must be perpendicular to blade
|
Ribbons compress and crumple Smooth ribbons do not form | - Block is too warm
- Slow and uneven rotations increase compression
- Paraffin is too sticky; needs to be harder
- Dull knife
- Knife clearance is too small
| - Block must be chilled well
- Use consistent wheel rotation to get even ribboning
- Need paraffin with higher melting point
- Change to fresh blade
- Increase knife clearance
|
Large holes, missing tissue, or mushy sections Parts of tissue not showing on slides | - Tissue not embedded flat; will not show during sectioning
- Tissue not processed properly and will not form a section (especially if center is raw)
- Under-processed portion of tissue bursts on contact with warm water
- Block faced too aggressively
| - Depending on issue/symptom, re-embed or re-process tissue as required
|
Ribbons stick to microtome or clothes Ribboning is difficult because sections attract themselves to everything | | - Use anti-static spray; cut smaller ribbons for better control; to avoid creating static, do NOT wipe microtome frequently and/or vigorously, especially with ParaPel®
|
Knife gouges out part of block Blade chops into block; tissue may be lost | - Tissue is loose in block
- Block not securely embedded to cassette
- Knife/other microtome parts not clamped down
- Block is not secure in block holder
- Aggressive facing with rapid wheel rotation
| - Re-embed tissue
- Re-embed block to properly secure to the cassette
- Tighten all clamps to verify all parts are properly secured
- Re-secure block in block holder
- Slow down
|
