Home Forums Explore Media Oil Painting Does water re-soften gesso on a panel?

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  • #1546898
    cdonham
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        I have been experimenting with preparing my own panels for painting.  Something happened today that I don’t understand.  I took a piece of HDF and applied several layers of Liquitex professional gesso.  I let this dry for 24 hours.  I saw something online about wet-sanding to get a smoother surface and decided to give it a try.  I took an atomizer and spritzed some water onto the panel.  I then took a damp 120 grit sanding sponge and proceeded to gently sand the panel in circular motions.  The topmost gesso seemed to turn back into a slurry as I gently sanded.

        Please help me to understand.  I thought gesso was a good base for acrylic as well as oil painting (I’m an oil painter).  It seems counter-intuitive that the gesso should dissolve even a little bit when spritzed with water.

        • Was it the fact that my gesso had not cured completely (it being only 24 hours since I applied the gesso)?  Would this happen even if the gesso had cured for a “long time”?
        • Was it that the sand paper was liberating dust that was then mixing with the water to dissolve?

        Why isn’t this a problem when painting with acrylics over gesso?

        Thanks

        Chris

        #1547481
        DebWDC
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            OK, I’ll hazard some guesses:

            ” It seems counter-intuitive that the gesso should dissolve even a little bit when spritzed with water.”

            Answer: your gesso (actually an acrylic-based primer) did not dissolve when spritzed with water. It only reacted when you first wet it, and then ground it with 120 grit to remove part of the top layer and make it smoother. You got it wet enough to make a slurry. This is not a spritz.

            “Was it the fact that my gesso had not cured completely (it being only 24 hours since I applied the gesso)?  Would this happen even if the gesso had cured for a “long time”?”

            Answer:  The short curing time may have contributed a little to this, but grinding the surface with a 120 grit was the main reason. If you had dry sanded it, material would still have been removed.

            “Was it that the sand paper was liberating dust that was then mixing with the water to dissolve?”

            Answer: Yes. That dust was the binding medium and the calcium “tooth.” Liquitex professional gesso is advertised as having a high tooth. Tooth is what wears out brushes and keeps brush manufacturers in business (only partly joking).

            The MITRA site has good information about materials and processes.

            ps – Chris, if you are using a wood product as a substrate, I think its important to seal all 6 sides before applying ground and painting.

            #1548873
            WFMartin
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                The water is not “re-softening” the coating of previously-applied, acrylic primer;  the residual “dust” created by the sanding process is simply mixing with your water, creating the “slurry”.   It’s as though you are creating a new batch of primer from the dust and the water.

                But, I see no particular advantage in performing this wet-sanding that you are doing.  I just dry-sand it. and then wipe off the residual dust using a damp paper towel.

                wfmartin. My Blog "Creative Realism"...
                https://williamfmartin.blogspot.com

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