Fig. 1From: Hybrid nanogels and their roles in eliminating soot stains from historical paper manuscriptsSamples of paper stained with soot and the cleaning process with the prepared nano minerals (ZnO, TiO2, and Fe3O4)/Carbopol Hybrid nanogel. A the accelerated aged stained paper samples. B Spatula to prepare high viscosity nanogels; C polyethylene sheet coverage; D removing gel layer with spatulaBack to article page