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Hi all,

Doing my first DIY bathroom tile job, just a 2x3m space, but have run into an issue with primer...

One of the walls is an external solid wall (Victorian property) and this wall was rendered, then skimmed with gypsum plaster (months ago). I heard that I needed to prime this wall before tile, so bought some Tilemaster Flexmaster primer which I diluted 3:1 and gave the wall 2 light coats, as per the instructions. This was a couple of days ago. On this wall I am only tile up to 1.3m, and the upper part of the wall is painted.

When I touch the primed surface, there is a slight tackiness to it, but there are dark areas and light areas (see photo below) and it feels a little more tacky in the light areas. When I press my finger onto the light areas for a couple of seconds and remove it, the primer sticks to my finger such that it creates a bubble on the wall when I fully detach from it. If I peel away the bubble, I am back to dry plaster underneath. Does this mean it has skinned over? The darker areas don't bubble in this way and the primer feels more attached to the plaster, although still has a (dry) tackiness to it. The light areas seem to be around 20% of the primed surface.

What to do? I have read some horror stories of tiles falling off the wall, so is this an issue I need to remedy before going further, or do I just need to wait longer for the primer to cure? I'm not in a huge rush, so can wait if need be. I have another 1m section of this wall to so, but thought I'd seek advice before priming that too.

Just to say, the wall was dry when I applied the primer, but with the weather recently the outside temperature has been 8-10C, so the wall was probably a similar temperature as no heating in the bathroom currently. I also lightly rubbed down the plaster with 80 grit sandpaper to key the surface before priming and removed dust with a damp sponge at least an hour before priming.

I will be using Tilemaster Setaflex S1 https://www.tilersforums.com/forums/tile-adhesive/ on this wall - which has been working great on other walls so far.

Any advice appreciated!

Thanks.
Alf

primer.jpg
 
OP
Alf_Laden
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Hi Lou,
I have done some more tile on the other walls, but I am a bit stumped on what to do with this primed wall - not sure if I need to remove all the primer and do it again given that some of it looks to have skinned.
Thanks,
Alf
 
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Alf_Laden
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If the primer has skinned and peeling , then yes remove it and use a weaker ratio.

Thanks for your reply, Dave. It looks like only parts of the wall (the lighter coloured areas in the picture) have skinned - so presumably I'd only need to remove those areas - I assume the rest is OK as it seems firm. I guess a scraper will be good enough to remove the skinned sections, or maybe some 80 grit sandpaper.

The manufacturer of the primer says to apply 2 coats, but I might just stick with one coat when I reapply again, as I originally thought the wall looked 'ready' after a single coat, which might explain why some of it skinned after the 2nd coat.
 
OP
Alf_Laden
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Spoke direct with Tilemaster Adhesives technical support, who advised the same as Dave above - remove any skinned primer (used a scraper) and then apply at a weaker ratio (went for 5:1) before applying a 2nd coat at the normal 3:1 ratio. They suggested that the plastered wall absorbed the water from the initial 3:1 primer mix too quickly due to high porosity.

Cheers Dave!
 

Dave

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Spoke direct with Tilemaster Adhesives technical support, who advised the same as Dave above - remove any skinned primer (used a scraper) and then apply at a weaker ratio (went for 5:1) before applying a 2nd coat at the normal 3:1 ratio. They suggested that the plastered wall absorbed the water from the initial 3:1 primer mix too quickly due to high porosity.

Cheers Dave!
Glad your sorted. 👍
 

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