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Finishing MDF


(Angus) #1

Hi TP community -

I would very much appreciate some advice/comments on how I can improve my finish on painted MDF using a water based approach. My goal is to achieve as close to a brush-less finish I can achieve with my limited experience and available time…

The materials, tools and process I have adopted (learnt from this community:grinning:) are:

Materials and tools
New unfinished Medite 18mm thick MDF panels
Mirka Abranet abrasives on Bosch GEX 125-150 random orbital sander and a Mirka block
Teknos Futura Aqua 3 Primer
Teknos Futura Aqua 20% sheen top coats
Two fussy blokes 5mm nap microfiber rollers sleeves, 100mm
Royal Langnickel golden taklon brushes for laying off

Process (along with corresponding image)
Primer coat with roller
Quite a heavy sand at 180p to flatten primer – not completely flat
Primer coat with roller
Sand quite heavy with 180-240p to flatten primer – not completely flat
Top coat applied with roller and lay-off with 75mm wide Royal Langnickel
Sand with 400p to flatten
Top coat applied with roller and lay-off with 75mm wide Royal Langnickel
Room temperature low 20’s with still air
Dust was removed after each sanding stage with a vacuum, microfiber cloth and finally a tack cloth
Drying time between all coats at least 12hrs majority 24hrs

Linked is a photo of the final finish. The photo was taken under direct light to expose the flaws - in flat / indirect light the brush marks are not visible.

Thanks in advance for your time and responding to my post.

Cheers
Angus


(Andy Crichton) #2

That’s pretty thorough!

Are you getting those brush marks with every coat? Check out the following to see if they make difference.

Could be the laying off brush is putting paint on, rather than levelling out what is there. ie Make sure your brush is clean not clogged.

You could be laying off when the paint is going off ie not being quite quick enough with laying off.

Maybe the paint is applied too thin, so try applying it a bit thicker to see if it flows out better.

Is the primer coat providing a non absorbent base for the topcoats to flow out well? As an experiment, try applying the topcoats over a glossy primer or old gloss paint. You may see better flow out of the topcoat. Also see how the sheen compares to your finish on the MDF. If it is considerably more shiny, the MDF primer you are using may need to toughen up!

Homework :slight_smile:


(Angus) #3

Thanks for responding Andy. Homework welcomed:)

You’ve made me realise that I have some Tikkurila Otex for another job (not started and totally the wrong colour for the current job). I’m thinking two coats of this would satisfy your suggestion to apply the top coat on a more robust/glossy substrate?

I’m have my suspicions that the sanding needed to flatten the primer and the primer itself is resulting in a porous surface. It not a particularly high-build primer, so I may try three coats.

Brush marks improve with each top coat.

I’ll also look at the various techniques you’ve suggested.

I’ll post back once I’ve made some progress.

Thanks again!

Angus