It did work but it took careful application. The first coat started drying very unevenly so I brushed it out while wet to get an even coat. Was nervous so applied a second coat. The end result was good. 3 years later the top coat is still intact ( but we don’t scrub the tiles).Today I did some shiny enamel paint. Same issue with first coat. . Will try sanding a bit more.

I had a similar problem to Helena who found it failed a scratch test.
It claims to adhere to difficult surfaces such as plastic. I followed the instructions and left it 3 days to dry. It did not stick and came off with any slight scratch. Even after 2 weeks in summer it still came off with any slight scratch. I found that the top coat adhered to the plastic better than the primer.

I had to paint all old laminated kitchen cupboards and found Grip Lock awesome I would never use any other primer. Along with a good prep this makes the paint stick with minimum sanding. I love this product. It is pricey but if you don't use it the paint just peels off like a coat and any job is ruined, so use Grip Lock it makes lifes tedious tasks effort free and rewarding .

Used on a bathroom with constantly peeling ceiling despite improved ventilation. Tenants never bothered to ventilate the bathroom properly. 2 years on after repainting it's still holding up well.

I have used Grip lock on our laminex kitchen cupboards as we wanted to change them but could not afford new ones. It worked a treat! I left it to dry for about 3 days before over coat with the new color. After the new paint dried for a couple of weeks it has been brilliant. Its been about 3 years now and I would say it has worked as good as any other painted surface. Fantastic stuff.
Washes out in water and its low odour. Also applies easy with a roller or brush.