A method of measuring strains very close to weld deposits has been developed using moiré fringe technique and mismatch gratings. It is necessary to compromise between accuracy and gauge length, but an accuracy of 100μin/in (‐10‐4) can be achieved with a gauge length of 0.2 in (5mm). Strains parallel to the weld deposit can be measured right up to the fusion line, but in the direction normal to the weld deposit the first strain reading is controlled by the gauge length, as defined by the distance between successive fr