Matt over silk... How much sanding is required?

Poiu · Post by **Poiu** » Sat Dec 18, 2021 3:26 pm

Hi all!
I am looking at fixing the walls that have a few nicks and re-painting all of them. All walls are painted with vinyl silk and we want to replace it with a matt finish.

I am planning to sand them, fix the odd spots with easyfill and then paint.
Now... How much sanding do I actually have to do? Is it just to scratch the surface of the existing silk paint or do I have to do some serious sanding? How do I know if I have done enough sanding? I am using 80 grit sand paper. Is it coarse enough?

dewaltdisney · Post by **dewaltdisney** » Sat Dec 18, 2021 3:54 pm

The thing with silk is that your roller will slip on the shiny surface so a nice key allows the new paint to stick on and roll out smooth. I tend to use wet and dry paper, not too fine a grit, and a bit of washing up liquid in the water helps to lubricate the paper and degrease the surface at the same time. I use it for wood trim mostly as it flattens old gloss of nicely but it will do the wall silk finish too.

DWD

Poiu · Post by **Poiu** » Sat Dec 18, 2021 4:06 pm

dewaltdisney wrote: ↑Sat Dec 18, 2021 3:54 pm The thing with silk is that your roller will slip on the shiny surface so a nice key allows the new paint to stick on and roll out smooth. I tend to use wet and dry paper, not too fine a grit, and a bit of washing up liquid in the water helps to lubricate the paper and degrease the surface at the same time. I use it for wood trim mostly as it flattens old gloss of nicely but it will do the wall silk finish too.

DWD

Hi DWD thanks foe the reply!
What grit of wet&dry would you suggest to use? And how do I know when I've done enough sanding? I dont want to spend a week sanding a room but I also don't want for the paint job to be complete sh#t

As I've said, at the moment I'm using 80 grit and it seems that it barely scratches it. I'm wondering if I'd should go for 60 or even less at this point.

wine~o · Post by **wine~o** » Sat Dec 18, 2021 6:26 pm

Save yourself a lot of elbow grease. Sugar soap the walls then give it a coat of Zinsser B-I-N , followed by a topcoat or 2 of your choice BIN is a bridging primer.

Poiu · Post by **Poiu** » Sat Dec 18, 2021 6:49 pm

wine~o wrote: ↑Sat Dec 18, 2021 6:26 pm Save yourself a lot of elbow grease. Sugar soap the walls then give it a coat of Zinsser B-I-N , followed by a topcoat or 2 of your choice BIN is a bridging primer.

The main reason why I am looking into the sanding option is that I will have to repeat the process in the whole house. BIN is at 20£/litre and 1L covers about 12m2... I'd be looking into spending hundreds of pounds just for that. Sanding seems to be the cheaper option even though I know it's going to be much messier and time consuming.

The thing is, everywhere it is mentioned that sanding is an option but they don't say how much sanding is actually required. That's what I'm not sure about.

wine~o · Post by **wine~o** » Sat Dec 18, 2021 6:51 pm

And how much is your time worth ???

dewaltdisney · Post by **dewaltdisney** » Sat Dec 18, 2021 6:57 pm

This not prepping a car panel, you are just breaking the silk surface, not removing the paint. You could use a Scotch pad to do it.

DWD

Poiu · Post by **Poiu** » Sat Dec 18, 2021 11:21 pm

wine~o wrote: ↑Sat Dec 18, 2021 6:51 pm And how much is your time worth ???

At the moment I can afford wasting my spare time

We have a lot to things to do in the house so we want to try to keep the costs down where possible.
I am trying to find the most cost effective way to do this regardless of the time it takes...

Poiu · Post by **Poiu** » Sun Dec 19, 2021 1:56 pm

Here a pic of the before and after sanding: should it be ok/too much/too little?

dewaltdisney · Post by **dewaltdisney** » Sun Dec 19, 2021 2:50 pm

Rub your fingers lightly over if they slip then it needs a bit more. If you can feel it grabbing slightly then it will be fine.

DWD

Tom d'Angler · Post by **Tom d'Angler** » Mon Dec 20, 2021 8:29 am

I've had problems in the past with matt crazing after it was painted over silk. I always sand lightly then give the surface one coat of Zinsser Gardz. The Gardz goes a lot further than B-I-N but, in my experience, does the same job over silk.

Croker · Post by **Croker** » Thu Dec 30, 2021 5:13 pm

Tom d'Angler wrote: ↑Mon Dec 20, 2021 8:29 am I've had problems in the past with matt crazing after it was painted over silk. I always sand lightly then give the surface one coat of Zinsser Gardz. The Gardz goes a lot further than B-I-N but, in my experience, does the same job over silk.

I was in a similar situation to the OP a while back, and after asking on here was directed to Zinsser Gardz. It was a huge job and I didn’t really fancy sanding it all first so just put the Gardz straight on followed the next day with the new matt paint. Worked a treat for me, and I agree that it goes a long long way (also a fair bit cheaper than BIN to begin with).

Definitely worth considering, though to be fair lightly sanding the old silk paint would be more cost effective.