Priming/undercoating mdf panels

ashe

Following on from my other post I have given the mdf panels I installed a coat of rustins primer 

was backbreaking and it took about 4 hours and 1.5L of primer. Cutting into the routed sections took forever with an angled brush! 

Happy to do it properly, but wondering if I need to do a second coat of this given that it's a little patchy looking? I'm hoping the answer is no 😂

I'll be painting this with probably 3 coats of Tikkurila Optiva 20 eggshell in dark blue (Denim) colour so curious if that will be enough or if I definitely need another undercoat first?

cheers 👌🏻

flashg67

IMO, primer/undercoat is just that and I can't remember using 2 coats on any of my projects!

theonlywayisup

I've only ever used Zinsser BIN on MDF and one coat was sufficient, looked worse than yours too! 

Grenage

I found oil-based undercoat worked better on MDF. Less raising off the fibres.

I'd just crack on with the top coats.

Mutton_Geoff

You shouldn't prime primer again. It's done it's job. What does it say on the tin?

Old fashioned painting involved primer, undercoat then topcoat. It didn't look finished until topcoat dried.

ashe

Mutton_Geoff said:

You shouldn't prime primer again. It's done it's job. What does it say on the tin?

Old fashioned painting involved primer, undercoat then topcoat. It didn't look finished until topcoat dried.

It says first coat primer second coat undercoat as it's 2 in 1

when I've googled I can see lot of sites saying two coats of primer for mdf but then lot of people saying they don't bother 

Ideally don't want to do 5 coats of paint 😂

ThisIsWeird

How well finished are the V-grooves (I appreciate they are nicer than plain Vs in your case)? I bought a sheet of waterproof MDF panelling like yours recently, and the grooves are very hairy from the routing, and will need significant sanding first, to get them smooth.

Check yours, and whether the primer has lifted any fibres as mentioned before. Give them a gentle denib if they have.

I'd then trial on one part (or a scrap piece?) going straight to the top coat - see how it goes.

ashe

ThisIsWeird said:

How well finished are the V-grooves (I appreciate they are nicer than plain Vs in your case)? I bought a sheet of waterproof MDF panelling like yours recently, and the grooves are very hairy from the routing, and will need significant sanding first, to get them smooth.

Check yours, and whether the primer has lifted any fibres as mentioned before. Give them a gentle denib if they have.

I'd then trial on one part (or a scrap piece?) going straight to the top coat - see how it goes.

They're pretty well done although their instructions did say to give a light sand which I did, they took the paint well, was more annoying making sure all the inside got coated though!