Good evening all,

A few weeks ago I skimmed our bathroom wall, let it dry (6weeks) and then primed it with neat BAL APD primer in preparation for tiling as per instructions. Once dry the primer could be peeled off easily like PVA does from your skin. I spoke with BAL technical support who advised on sanding it back, stiff brushing the dust off and re-priming with a 1:1 dilute.

So, I did the above as advised but the problem persists: If I stick a piece of tape to the wall i pulls away easily bringing the primer 'skin' with it. The wall was not dusty when the primer was applied - it was well brushed, wiped with a wet cloth and allowed to dry.

What am I doing wrong?

For information, I intend to tank it (BAL WP1) before putting up glass tiles (BAL Mosaic Fix).

Merry Christmas!

BJ

Sounds like dilution is wrong and so not absorbing, try a small area at 2:1 maybe see how that dries

Infact I take that back, I'm confusing it with sbr, you could still try it tho to rule that out.

Thanks Mattle40,

Just to confirm, you mean dilute it further? I have tried neat and 1:1 - so now try 2 parts water to 1 APD?

Would you then do a second coat neat?

bj

Merry Christmas to you too, imo neat primer is a no no. It will just form a skin on the surface, skim should be abraded to give a key, I don't use bal but even 1:1 seems to strong to me. I use Mapei primer G, and dilute it 3:1 the primer needs to soak into the skim to a degree, to form an anchor. Hope this helps BJ

Thanks Phil,

I shall try 3:1 over 2:1 as I reeeeaaallly don't want to have to strip it down a third time!

What concentration would you do the second coat? I will be using a cement based adhesive so I want to avoid reaction issues.

bj

(sorry if this repeat-posts, being unregustered it is a bit confusing as to when these posts appear!).

Sorry I was thinking of Bal bond which is SBR styrene butamien rubber. As opposed to APD acrylic polymer dispersion.

I'm with Phil and 2 coats of 3-1 or even 4-1 is usually enough .

If you wet the wall after the required drying time of the primer and the wall
Substrate wets up after a few mins then not enough primer.

Originally Posted by Phil Hobson

Sorry I was thinking of Bal bond which is SBR styrene butamien rubber. As opposed to APD acrylic polymer dispersion.

Haha same mistake, fools never differ

I think the principle is the same, as I don't use Bal I can't comment on APD, but imo the abrading of the skim is essential, especially with a highly polished finish. Just to open up the surface, (wire brush, or I prefare the diamond hand held pad).

As per Dave and Phil, dilute to 3:1 or 4:1 as a minimum for priming. Merry Christmas and happy sanding!

There are primers that recommend 5-1 dilution. Id mix it 4-1, and try it on a small area ONLY, and see how it takes. When properly primed, you can lick your finger and touch the wall. If you see a dark wet patch, its not primed enough.

We often say stick to the manufacturers recomm, but clearly this is not the case here as Bal suggest neat Apd or 50/50...wonder why.????

My question is when are the manufacturers going to be held responsible for the advice they give out?
If you dilute 3-1 4-1 5-1 and you have a problem they then say ahhhh we told you 2-1. To be honest I have so many issues with manufacturers I am just going to shut up.

Thank you all for your replies and many apologies for not getting back sooner.

Following your advice, I diluted the primer to (I estimate) between 1:6 and 1:8. I applied it to a test area of the wall and after approximately 15-20 coats the substrate was no longer taking in any moisture. I then repeated the "tape-test" using a lowish tack masking tape and still the skin came off easily.

I know have no clue what to do.

For information, when I originally primed the wall I also did the adjacent walls (not bare gypsum). When I do the "tape-test" on these walls nothing comes away with the tape (not even with duct tape).

Any other ideas? My sense of humour is begining to fail somewhat.

bJ

Try giving the skim/plaster a light sanding first before applying the primer so that it has something to key too, it could be that the skim has been over trowled, I have spoken to decoraters that have had this problem with paint running off walls before... not gospel but maybe worth a try.

If the plaster has been over troweled it can glaze the plaster and would need a fine sand papering the break the surface.