Paint Sweating on new MDF Shelves General decorating topics, questions and answers. find help, tips and advice on completing your decorating projects

[DasSmithStar]

I am trying to apply a coat of quick dry satin white paint to some new MDF shelves with a foam roller, but the paint is pulling apart from itself in what looks like sweating or that effect of you tried to paint onto glass (picture attached).

We have sealed the wood with sealant and painted an undercoat on before this coat.

Please help!

[DaveyTed]

I presume by "quick drying" you are using a water based satin. Assuming the undercoat surface has completely dried and is not greasy could it be that you are "overworking" the paint? Water based needs to be applied quickly and not reworked by running the roller back over the surface or you may be picking up paint as it starts to surface dry.
Ignore me if I'm going over what you already know.
Hope you get sorted.

[Nick-Horn]

Hi there,
I'm new to this forum. Basically joined to learn a bit about problems people are having with paint. I work for a small paint manufacturer so it's a bit of R&D for me.
But from what I have learnt from the chemists I work with the problem your having could be down to the ingredients used in producing MDF.
The effect your having looks like something they call sissing. This is where the wet film is pushed away from the substrate. Unable to penetrate or adhere. A lot of products will not work on MDF for this reason. Especially water based coatings.
Or it could defiantly be greasy any oil or was will cause that same look.
There are a few high quality products that will work.
But ideally you will probably have to go back to bare wood abrade the surface to increase the surface area and allow the paint to penetrate into the substrate.
Some sealing products will only make it worse. We never recommend people to use them especially things like PVA or cheap emultions as a mist coat.

Hopefully this may help.
And I got my first post out of the way!!
:-)

[Nick-Horn]

Hi there,
I'm new to this forum. Basically joined to learn a bit about problems people are having with paint. I work for a small paint manufacturer so it's a bit of R&D for me.
But from what I have learnt from the chemists I work with the problem your having could be down to the ingredients used in producing MDF.
The effect your having looks like something they call sissing. This is where the wet film is pushed away from the substrate. Unable to penetrate or adhere. A lot of products will not work on MDF for this reason. Especially water based coatings.
Or it could defiantly be greasy any oil or was will cause that same look.
There are a few high quality products that will work.
But ideally you will probably have to go back to bare wood abrade the surface to increase the surface area and allow the paint to penetrate into the substrate.
Some sealing products will only make it worse. We never recommend people to use them especially things like PVA or cheap emultions as a mist coat.

Hopefully this may help.
And I got my first post out of the way!!
:-)