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Brittle / hard block (crumbles or shatters)
Also known as: over-processed block, chalky sections
What it looks like
Sections crumble, shatter or chip; tissue looks dry, chalky and over-hard.
Where it usually appears: Over-processed, over-dehydrated tissue or prolonged time in hot wax.
Likely causes
- Over-dehydration / over-clearing (excess time in alcohols/clearant)
- Prolonged or too-hot paraffin infiltration
- Naturally dense/calcified tissue
- Delayed fixation followed by aggressive processing
Immediate checks
- Soak the block face on ice-water for a few minutes to rehydrate slightly before cutting
- Reduce cutting speed
- Surface-decalcify genuinely calcified tissue if appropriate
Corrective action
- Face, soak and re-cut
- Review and shorten the processing schedule for delicate specimens
Preventive action
- Use tissue-appropriate processing schedules (short for small biopsies)
- Avoid excessive alcohol/clearant dwell times
- Keep wax baths at recommended temperature
This atlas is for educational purposes for laboratory professionals. It does not replace your institutional SOPs, manufacturer instructions, validated protocols or pathologist judgment. Adapt any action to your laboratory and equipment.
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