Several possible causes, from simple to serious:

Quick diagnosis:

Simple fix (Check first):

  • When was last refill? (If >8 weeks, it’s normal)
  • Is this new to you or normal pattern?
  • Has room temperature changed? (Warmer room = faster loss)

Most likely cause:

  • Normal evaporation pattern for your dewar
  • Solution: Adjust refill schedule

Potential issues:

  1. Partial vacuum loss (30% chance)
    • Symptom: Gradual increase in evaporation over weeks
    • Solution: Professional inspection
    • Cost: £100-200
  2. Seal degradation (20% chance)
    • Symptom: Faster than normal loss, gradual worsening
    • Solution: Gasket replacement
    • Cost: £75-200
  3. Dewar age (20% chance)
    • Old equipment naturally loses some insulation efficiency
    • Solution: Consider replacement
    • Timeline: 10-15 year lifespan
  4. High ambient temperature (20% chance)
    • Warm room accelerates evaporation
    • Solution: Improve air conditioning/ventilation
    • Impact: Can double evaporation rate in 30°C+ environments
  5. Leak in inner vessel (10% chance, rare)
    • Symptom: Rapid catastrophic failure
    • Solution: Equipment replacement
    • Cost: Full replacement needed

Action plan:

  1. Track refill frequency carefully (keep log)
  2. If increased >25% from baseline, seek inspection
  3. Don’t ignore problem (may indicate serious issue)
  4. Have backup dry shipper ready for emergencies