Primer old plaster before patching?


Old 06-04-09, 06:21 PM
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Primer old plaster before patching?

Its been recommended to me that I prime my old paster with a shellac-based or alkyd primer prior to patching with setting compound. Is this extra step and expense necessary?
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Old 06-04-09, 06:43 PM
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Yes. Read this page and then click on "cracks" on the left boxes:

Getting Your Plaster Surface Ready For Repair

Be safe, G
Old 06-04-09, 08:31 PM
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The webpage reads, " may choose to brush on a coat of fast drying oil-based primer/stainkiller for extra security." So it is a judgment call I take it.
Old 06-05-09, 03:54 AM
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What shape is the plaster in?
If there is any chalk/dust that can't be completely removed - use primer.
Old 06-05-09, 08:16 AM
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Thanks for the reply. The old plaster is tight and clean. The situation is that I'm removing 5/16" laminate wall panels and then scraping away the backer glue cauing me to lose chunks of plaster.

I think I'll continue to scrape away any loose stuff, dust with a whisk broom, mist the old plaster with water and then apply the new stuff. On any deep areas I'm embedding mesh tape.
Old 06-05-09, 01:35 PM
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There is a product called plaster weld. You can get it at sherwin williams. You put it on the sandy areas of plaster and it makes it hard as a rock.
Old 06-05-09, 03:19 PM
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Thanks for the responses. I couldn't find plaster weld so I did picked up a 13 oz. spray can of shellac-based primer made by Zinnser at Home Depot. I'll spot prime any areas that are especially sandy and approach it that way.

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