S. No. Etching Reagent Composition Application Method Time Taken For Restoration Of Marks (minutes) Comments
1 Standard reagent 19 g FeCl3 + 6 ml conc. HCl + 100 ml dist. H2O The reagent was swabbed over the obliterated surface. 45- 60 min. The restoration was about 60-70% in 45-60 min.
2 Etching reagent 1 20 ml conc. HNO3 + saturated solution of K2Cr2O7 The etching reagent was applied on the obliterated surface by swabbing. 5 min. The restoration was about 70% in 5 min.
3 Etching reagent 2 20 ml conc.  HNO3 + 4g KMnO4 in 100 m dist. H20 The etching reagent was applied on the obliterated surface by swabbing. 10-13 min. The restoration was about 65% in 10-13 min
4 Etching reagent 3 10 g FeCl3 + 20 ml glacial CH3COOH + 100 ml dist. H2O The reagent was swabbed over the obliterated surface. 20 min. The restoration was up to 85% in 20 min
5 Etching reagent 4 12 g FeCl3 + 15 ml glacial CH3COOH + 100 ml dist. H2O + 2 ml HNO3 The etching reagent was applied on the obliterated surface by swabbing. 30 min. The restoration was up to 90% in 30 min.
6 Etching reagent 5 10 ml conc. HCl + 25 ml glacial CH3COOH Obliterated surface wad swabbed by the reagent until restoration occurred. 10 – 15 min. The restoration was about 75% in 15 min.
7 Etching reagent 6 12 g CuCl2 +10 ml conc. CH3COOH + 100 ml dist. H2O The reagent was swabbed over the obliterated surface. 35 min. No restoration of marks occurred.
8 Etching reagent7 12 g FeCl3 +7 ml conc. HCl + 50 ml C2H5OH + 50 ml dist H2O Obliterated surface wad swabbed by the reagent until restoration occurred. 35 min. The restoration was about 75% in 35 min.
9 Etching reagent 8 12 g FeCl3 + 20 ml NH3 solu. + 50 ml H2O The etching reagent was applied on the obliterated surface by swabbing. 15 min. The restoration was about 70-80% in 15 min.
10 Etching reagent 9 20 ml NH3 solu. + 20 ml conc. HCl + 50 ml dist H2O Obliterated surface wad swabbed by the reagent until restoration occurred. 20 min. The restoration was up to 90% in 20 min
(Observation shown in Table 1 emphasized that the etching reagent 3 gives best result. marks restored were better visible and took less time in restoration than that of standard reagent.)
Table 1: Relative efficiency of the metallurgical reagent in recovering marks erased by grinding.