Scuff x on MDF, which primer?

[User1234567890]

Morning all, I have a large MDF window sill that needs painting. I'm going to try the Scuff X as it is quite a high traffic area in a busy house. The MDF is primed, but there are areas of it that are bare MDF and have been sanded to shape and there are lots of scrapes and dirty marks from fitting the sill. There are also a number of screw holes that will be filled with Ronseal high performance wood filler. So, if I get this Scuff X paint, what would be the best primer to use? Is it wise to seal the countersunk screw holes before filling them?

I've already got some Leyland trade Acrylic undercoat Primer, but wasn't sure if that would play nice with the MDF, (as little sanding and reciting as possible for the cut/sanded edges) and also something that plays nice with the Scuff X, so any recommendations welcome, thanks

 

[Scally-Ho]

Hasving encountered a few disasters with MDF in the past due to swelling, I now only use oil-based primers on the material and also slightly thinned too. In my experience any water on a cut/sanded MDF surface will usually end in tears.

 

[User1234567890]

Hasving encountered a few disasters with MDF in the past due to swelling, I now only use oil-based primers on the material and also slightly thinned too. In my experience any water on a cut/sanded MDF surface will usually end in tears.

Thanks. I have had the same thing happen, which is why I'm asking here. I was thinking zinsser bin, but wasn't sure if it was ok with Scuff x? I know Rustin's do an MDF sealer that is water based that seems to get good reviews, but I also saw that some people were forever re-coating and then sanding back. This is a moisture resistant MDF is that makes any difference?

Would an oil based primer be ok for scuff x? And if so, which would you recommend, thanks.

 

[opps]

For many years, my bread and butter was hand painting MDF.

It is a myth that MDF is flawless. It has parallel score marks running along its length. I guess that they run it through a big drum sander.

I used Leyland Trade acrylic primer, knowing that I would have to then sand that flat. I used the paint as a visual indicator. Once I could no longer see the manufacturer's score marks, I was content that it was sufficiently flat. The following image shows the degree to which I would sand it back.



I would then apply two coats of oil based eggshell. I was happy that the sanded MDF was still slightly porous. It helped the eggshell soak in slightly and enable me to get even colour coverage in two coats.

I only had one customer specify a water based finish. I used Dulux Trade oil based primer. Sanding time was only about 10% shorter, but I had to wait longer before sanding it. I had to wait three days before applying the water based eggshell. Even then, there were still fisheyes that required me to pull the paint pad over the surface twice.

I did once try BIN. The unit was 4m long. The BIN left awful stipple marks. What should have been 1.5 days to sand back flat took 3 days and about 150% more abrasives.

MR MDF typically has a flatter finish. But even that has score marks. The cut edges are less porous though and often more crisp.

Personally, I would not entertain the idea of (hand painted) water based paint over water based primer, but I guess it depends on the quality of finish that you are happy with.

 

[User1234567890]

Thanks, the only reason that we are going for a water based finish, is so it doesn't go yellow after a few months. I believe that the scuff x is pretty tough for this kind of thing? What other kinds of paints are there for this application, that are pretty hard wearing and can be painted on with a brush, with minimal brush marks and doesn't go yellow?

I have used bin a few times and have got about half/third of a tin somewhere. I don't recall it being difficult to sand, but what I do remember is that you have to get it on quick, and it doesn't half stink!

 

[User1234567890]

Dug out the bin primer and did one end where I'd shaped it and it only raised the fibres a little bit, they sanded back nicely, so gave it a full coat, applied with a roller and laid (layed?) off with a 3" soft brush. The only issue I encountered was that, because it's a long sill, about 4m in total, and the temp was around 23c+, I got some dragging/sticking when laying it off, and could have done with something to extend the working time. It was drying faster than I could smooth it, so there were some less than smooth areas, because of that. I left it over night and gave it a sand this morning and it came up really nice. It will definitely need at least one more coat, as some of the areas where it was back to bare MDF, are showing as darker patches, but other than that, it's all good.