Calcium analysis ofCucurbitaembryos was carried out on samples dry‐ashed in porcelain crucibles. The atomic absorption procedure gave precise and repeatable results for most sample sizes but very small samples in the range 0.025–0.05 g persistently gave higher measured Ca concentration. The problem originated from an interaction of the sample with the crucibles and was manifested in small samples because of the increased surface contact between the samples and the crucibles. The interaction produced a change in the ash mineral complement relative to that of the larger samples and this change resulted in enhanced Ca signal in atomic absorption analysis.