need some painters advice

[Brian Ashton]

So I've decided to paint... What I've discovered is the paint peals very easily off the wall with a putty knife. I've been able to sand and scrape down to a very hard, by the feel of it, base layer that looks like it has very good adhesion to the drywall. I suspect that this base layer is oil based.

So what do I need to do to get the new latex paint to stick well to the base layer, unlike what I just pealed off. Do I need a primer, should I sand or just wash with tsp... What say you.

[David Gilbert]

My suggestion would be to first go to a paint store and ask them this question. My thought is that if the base paint is oil base so the latex doesn't want to stick then you do need an effective primer. For most wood finishing, shellac is the finish that lots of folks use to transition from one kind of finish to another. Here in the states you can buy a shellac based primer call "Bin" that is very effective. I know that they also have a water based version but don't know how that would work.

Good luck with the painting!

David

[Rich Engelhardt]

I've been able to sand and scrape down to a very hard, by the feel of it, base layer that looks like it has very good adhesion to the drywall. I suspect that this base layer is oil based.
If the walls are drywall, then it's a good bet what you're down to is an old gloss or semi gloss oil that was painted over without being scuff sanded first. The lack of adhesion you're seeing is a classic symptom.

If the walls are old plaster, then you may be down to the plaster coat - which is a hard slick almost paint like in appearance surface.
If indeed the walls turn out to be plaster & you're down to the white coat, you need to avoid using anything oil based on it as a primer - such as Kilz.
You also don't want to wash it as doing so will spread the lime the plaster is giving up,, all over the surface.
Lime and oil based don't play well together.
Heck lime and anything don't play well together - but - PVA (poly vinly acetate) primers fare the best.
B*I*N and/or any shellac based product on plaster only works so-so.
"Old school" rule of thumb for plaster was to size it first, then prime, then finish. The size was nothing more than hide glue.
W/the advnet of cheap PVA primers, they became the product of choice for priming old or new plaster.

B*I*N a pigmented shellac will work fine on an old gloss or semi gloss paint. Being old school, I'd still scuff sand first if the walls are smooth enough to sand. If they have a texture that prevents sanding, the B*I*N will still work fine.

As mentioned above, Zinsser (the maker of B*I*N) also offers a few other waterborne products that can be used on either old paint or old plaster (or new plaster for that matter - which is pretty rare these days).
I can't in good concience recommend any Zinsser product, other than their shellacs. I've recently had too many problems with them.

Kilz makes similar waterborne primers - however - they (Kilz) recommend sanding old gloss or semi gloss finishes prior to using them.
Zinsser claims their products can go directly over an old gloss or semi gloss sruface w/out any sanding.
I found through bitter recent experience that's no longer the case.

We (my wife and I were/are doing the rehab of a 50's era house) switched over from the waterborn Zinsser products to Glidden Gripper primer.
The Gripper, so far, has lived up to all it's claims of sticking to a gloss or semi gloss surface w/out sanding. It runs nearly double the price though - but - it works.

All three lines, Zinsser, Kilz, Glidden Gripper should be available to you down under.

[Brian Ashton]

The guys. Now to get the rollers out

[Phil Thien]

I'd use a product called XIM 400. It is a primer/bonder.

http://www.ximbonder.com/products_detail.asp?id=30

It is part primer, part glue. I typically buy it in white, and then have it tinted sort of close to my final color.

I'd test a small area first by scuffing up the underlying paint, then apply XIM. Wait 24 hours and try to scrape it off with your fingernail.

[Myk Rian]

Kilz. This stuff sticks to everything, and everything sticks to it.