Advice about primers and undercoat please

[wmrcomputers]

I've built something from mdf, and I intend to paint it gloss black with a roller.

I have spent the last two hours on Google learning about primers and undercoat but there are very mixed opinions. Some say that a primer sand primer then gloss is okay, others say just use undercoat. Some also say that if doing 2 coats of top coat, to just think of the first top coat as the undercoat.

Now my head hurts so if anyone has any experience in this matter I would really appreciate your feedback.

Cue gramaisc suggesting ibuprofen

 

[Gramaisc]

I suggest taking ibuprofen.

I never done this, but the word on the street is that MDF is prone to cause pinholes in the top finish, due to its absorbency. There are many 'special' MDF primers* available that are supposed to counter this. I would suggest that you experiment on some off-cuts - the roller could be kept wet by covering in cling-film whilst you assess the situation..

*e.g., http://www.international-paints.co.uk/products/info/quick_drying_mdf_primer.jsp

Supplementary question why is there apparently only MDF - medium density fibreboard, never high or low density..?

 

[wmrcomputers]

Interesting question which I've considered myself before. I think there must have been low and high before, but due to overall flexibility in use for the medium the demand for low and high ceased, maybe??

 

[Jonah]

If I were you, I would look at the gloss paint you are going to use and follow the manufacturers application instructions. If it says primer then undercoat then that's what you do. Normally the people who make the paint know what the paint needs.

And yes, I know it may be a sales "opportunity" for them but I have cut corners in the past and regretted it.

And one piece of advice. Got to the Dulux Decorator Centre on Greyfriars and buy trade paint. It's more expensive but far better quality.

 

[wmrcomputers]

Some good info there bigblue - thank you.

 

[Goldilox]

Supplementary question why is there apparently only MDF - medium density fibreboard, never high or low density..?

Low density is better known as chipboard, high density as hardboard.
http://en.wikipedia.org/wiki/Fiberboard
Wiki

 

[wmrcomputers]

Ahhhhhh I see. Now we know

 

[Gramaisc]

Low density is better known as chipboard, high density as hardboard.

Wiki

Indeed, so why not just chipboard, fibreboard and hardboard? It just seems like an over-specific designation intended to differentiate it from materials that it's not going to be confused with anyway..

 

[wmrcomputers]

I agree - although I might ask where the LDC or HDH is at B&Q