You are reading a single comment by @cozzzzzzzz and its replies.
Click here to read the full conversation.
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
cozzzzzzzz
You seem to be on the right track, scraping with a very sharp blade would be a good thing to try. With unpainted plaster it can be very absorbent so you might struggle to get the primer from the pores of the plaster.
If it's relatively fresh you might have some luck wetting it a bit and running a steel edge over it to try and 'turn' the surface. Depends how long it's been dry.
Regarding the primer, yes it's for grip both to the substrate and for the next coat. Paint has a lot of different qualities that you can start to differentiate with experience. I like to prime and then undercoat with something a bit thicker for opacity and levelling. Oil based paints used to be great for this, it was like icing skirting boards with Dulux oil based eggshell.