Dear Widi.

I don´t know about decreasing background staining using ethanol, except as medium for dissolving sudan black.

For the staining of paraffin slides, it is essential to rehydrate your sections. After removal of paraffin using xylene (hydrophobic compound) you have to slowly rehydrate your sections by putting them into decreasing concentrations of ethanol (= increasing concentrations of water), since the histochemical staining is mostly carried out in hydrous media (PBS, H2O). Otherwise staining will be unpossible or uneven, since antibodies and other essential compounds solved in hydrous media will not be able to bind to a hydrophobic surface.

If you coverslip your sections in a xylene or toluene (hydrophobic compounds) containing medium, then before coversliping you have to dehydrate your sections by putting them in increasing concentrations of ethanol (= decreasing concentration of water) and as last step xylene to completely remove hydrous compounds from your slide. Otherwise the section will not be completely soaked and bubbles will appear.

If you coverslip in a hydrous solution, mostly done for fluorescent stainings (f.e. citifluor) dehydrating is not necessary.

Hope this explenation is helpful.

Greetings

Dear Widi.

I don´t know about decreasing background staining using ethanol, except as medium for dissolving sudan black.

For the staining of paraffin slides, it is essential to rehydrate your sections. After removal of paraffin using xylene (hydrophobic compound) you have to slowly rehydrate your sections by putting them into decreasing concentrations of ethanol (= increasing concentrations of water), since the histochemical staining is mostly carried out in hydrous media (PBS, H2O). Otherwise staining will be unpossible or uneven, since antibodies and other essential compounds solved in hydrous media will not be able to bind to a hydrophobic surface.

If you coverslip your sections in a xylene or toluene (hydrophobic compounds) containing medium, then before coversliping you have to dehydrate your sections by putting them in increasing concentrations of ethanol (= decreasing concentration of water) and as last step xylene to completely remove hydrous compounds from your slide. Otherwise the section will not be completely soaked and bubbles will appear.

If you coverslip in a hydrous solution, mostly done for fluorescent stainings (f.e. citifluor) dehydrating is not necessary.

Hope this explenation is helpful.

Greetings

Thank you so much for answering my question Ma am, it's very helpful :-)

Nice explanation by Dr Marcia ..

Hello Widi,

Marcia has done justice to the explanation.

However, to add a note about the decreasing background staining using ethanol; ethanol is able to bleach most stains, and this somewhat improves the background of the stained slides.