Pashtet

Hi everyone, I am looking for a bit of help with a chemistry question. I am doing a lot of metallographic etching (weld cross sections) and are currently using two different diluted acids: 1. For steel metallographic samples - 10% ammonium persulfate in water 2. For aluminum metallographic samples - 10% NaOH in water Both liquids are very thin (low viscosity) and run off the samples so I have to constantly reapply the acid. I would like to make them thicker (e.g. paint or gel viscosity level). I was thinking of using some off the shelf water thickeners like gelatin. However, I do not know if this will create any unexpected reactions. I do not remember much from the high school/university chemistry courses (I am a mechanical engineer by training). Can somebody help me to predict what reactions I am going to see or suggest some other thickeners? I would really appreciate any suggestions, Thanks!