Fig. 4From: Green chitosan: thiourea dioxide cleaning gel for manganese stains on granite and glass substratesCleaning assay performed on stained granite at St. Tiago church. Assays were done inside the labelled yellow marks; A1 and A2 are images of stained granite; B1 and B2 are images of removed stain. A2 and B2 images were taken by Dino-lite (×435 magnification)Back to article page