PROBLEM-REASON-REMEDY

• Brittle or hard tissue

  REASON:

  • Prolonged fixation, dehydration, clearing, paraffin infiltration
  • Overheated paraffin oven
  • Drying out of tissue before actual fixation
• Brittle or hard tissue

  REMEDY:

  • Softened by soaking in a small dish or bowl containing water with detergent, phenol or Molliflex
• Clearing agent turns milky as soon as tissue is placed in it

  REASON:

  • Water not completely removed
  • Incomplete dehydration
• Clearing agent turns milky as soon as tissue is placed in it

  REMEDY:

  • Repeat dehydration with absolute alcohol
  • Clear again
• On trimming, tissue smells of clearing agent

  REASON:

  • Clearing agent not completely removed
  • Insufficient impregnation
• On trimming, tissue smells of clearing agent

  REMEDY:

  • Block is trimmed down nearest to the tissue
  • Remaining wax is melted on embedding oven
  • Paraffin impregnation is repeated
  • Change paraffin at least once before blocking
• Tissue is opaque, section cutting is difficult due to presence of alcohol

  REASON:

  • Insufficient clearing
• Tissue is opaque, section cutting is difficult due to presence of alcohol

  REMEDY:

  • Repeat clearing
  • If object has already been embedded, prolong clearing up to 12 hours, then re-embed
• Tissue shrinks away from wax when trimmed

  REASON:

  • Insufficient dehydration
  • Incomplete clearing and impregnation
• Tissue shrinks away from wax when trimmed

  REMEDY:

  • Repeat whole procedure
• Tissue is soft when block is trimmed

  REASON:

  • Incomplete fixation
• Tissue is soft when block is trimmed

  REMEDY:

  • Repeat whole procedure
• Air holes found on tissue during trimming

  REASON:

  • Incomplete impregnation
• Air holes found on tissue during trimming

  REMEDY:

  • Repeat impregnation
• On trimming, wax appears crystalline

  REASON:

  • Contaminated wax
  • Block not cooled rapidly enough
• On trimming, wax appears crystalline

  REMEDY:

  • Re-embed in freshly filtered wax
• Paraffin block, after cooling, is moist and crumbles

  REASON:

  • Insufficient paraffin impregnation
• Paraffin block, after cooling, is moist and crumbles

  REMEDY:

  • Repeat paraffin impregnation, then re-embed
• Sections fail to form ribbons

  REASON:

  • Surfaces and edges of the block are not parallel

  REMEDY:

  • Re-trim the block
• Sections fail to form ribbons

  REASON:

  • Horizontal surface of the block is not parallel to the knife

  REMEDY:

  • Re-adjust and re-orient the block
• Sections fail to form ribbons

  REASON:

  • Paraffin wax is too hard

  REMEDY:

  • Coat horizontal edges of the block with wax of lower melting point
• Sections fail to form ribbons

  REASON:

  • Knife is tilted too much

  REMEDY:

  • Reduce tilt
• Sections fail to form ribbons

  REASON:

  • Sections are too thick

  REMEDY:

  • Re-adjust the thickness of the sections
• Sections fail to form ribbons

  REASON:

  • Knife is dull

  REMEDY:

  • Hone and strop
• Sections roll up on cutting so that they adhere and get broken against the knife edge

  REASON:

  • Knife is blunt

  REMEDY:

  • Sharpen the knife
• Sections roll up on cutting so that they adhere and get broken against the knife edge

  REASON:

  • Tilt of knife is too great

  REMEDY:

  • Reduce the tilt
• Sections roll up on cutting so that they adhere and get broken against the knife edge

  REASON:

  • Knife edge is dirty

  REMEDY:

  • Clean the knife edge
• Ribbon is curved, crooked or uneven instead of straight

  REASON:

  • Blunt of dull spot on the knife = irregular knife edge

  REMEDY:

  • Adjust the knife so that knife edge will present a uniformly sharp edge to the block
  • Sharpen
• Ribbon is curved, crooked or uneven instead of straight

  REASON:

  • Edges of the block are not parallel but round or wedge shape

  REMEDY:

  • Re-trim the block
• Ribbon is curved, crooked or uneven instead of straight

  REASON:

  • Knife is not parallel to the block

  REMEDY:

  • Readjust knife and block
• Ribbon is curved, crooked or uneven instead of straight

  REASON:

  • Paraffin is impure

  REMEDY:

  • Repeat impregnation using pure wax
• Sections are compressed, wrinkled, or jammed

  REASON:

  • Knife is blunt or dull

  REMEDY:

  • Re-sharpen the knife
• Sections are compressed, wrinkled, or jammed

  REASON:

  • Paraffin block is warm and soft

  REMEDY:

  • Cool the block on ice water until firm
• Sections are compressed, wrinkled, or jammed

  REASON:

  • Knife edge is coated with paraffin

  REMEDY:

  • Clean the knife edge
• Sections are compressed, wrinkled, or jammed

  REASON:

  • Sections are too thin

  REMEDY:

  • Readjust thickness of section
• Sections are compressed, wrinkled, or jammed

  REASON:

  • Microtome set screw is loose

  REMEDY:

  • Tighten the screw
• Sections are compressed, wrinkled, or jammed

  REASON:

  • Tilt of knife is too vertical

  REMEDY:

  • Reduce the tilt
• Sections are squashed (width of each section is less than that of block)

  REASON:

  • Bevel of knife is lost due to incorrect sharpening

  REMEDY:

  • Re-sharpen, using a knife back or automatic knife sharpener
• A hole is formed in the section

  REASON:

  • Bubble or dirt formed in the embedding medium

  REMEDY:

  • Re-embed in freshly filtered wax if necessary
• A hole is formed in the section

  REASON:

  • Hard spot in tissue due to calcium

  REMEDY:

  • Once embedded in paraffin wax, decalcification is impractical; use a base-sledge microtome with a wedge knife