Problems with placing samples in ice 
- Non-uniform ice contact: variable sample temperature
- Disorganized samples, wet labels
- Shifting, sinking tubes; contamination risk
- Non-reproducible method
The thermoconductive rack solution 
- All samples <4°C and uniform in temperature (+/- 0.1°C)
- Samples organized, secure and dry
- All tubes upright and indexed
- Reproducible method