Table 1.

 Spore number on grids in independent experiments (1–6) using a spore suspension of 10⁸ spores per ml. In experiments 1–4, the shelf life of the alcian blue solution was tested at defined intervals of storage (d = days). In experiments 5 and 6, different batches of alcian blue solution were used than in experiments 1–4

Experiment	Particles/square	Interquartile range	No. Grids
1 (d 0)	11	2	3
2 (d 30)	12	1	3
3 (d 90)	12	1	3
4 (d 180)	10	0.5	3
5	10	0	3
6	10	0.5	3