Finishing Smoothing / Painting MDF cut edges

[hunggaur]

hi folks this may have been asnwered 100 times before and i am sorry if it has but i could not fined the answer in the search results.

i am looking to build a fitted unit out of MDF which will then be painted.

my problem is that when i have done this in the past the cut edges have always looked rough no matter how much i have sanded them. Is there a way of getting them as smooth as the top surface of the MDF.

i once heard that you should paint the edges with PVA then re sand with 600 grit is this true ????

any advise always welcomed

kind regards

jon

 

[Howie]

Hi Jon
I have tried all types of methods to get MDF edges smooth including the PVA idea. The method I have found which works best is to simply use a two part woodfiller onto the edges and then sand down with 120 grade paper. Then undercoat and paint.
Works for me.
Paul

 

[9fingers]

1. Ideally use MRMDF - it seems to have more resin in it or something like that and cut edges are smoother.

2. After a first sanding, coat with shellac/sanding sealer and rub down with fine grit papers to 320/400 or better

3. Paint with several coats de-nibbing as you go.

4. If possible, avoid high gloss paint.

5. Avoid water based paint if you are brushing - I had a horrible experience with it recently as brush marks would not go.

hth

Bob

 

[moz]

Shellac works well, sanding before then after with 320g silicone carbide (resists clogging better than aluminium oxide). I mix up my own blonde de-waxed shellac. I've heard the waxes in other types can be a problem with subsequent finishing. I have experimented with others with no problem but don't like to take the risk with my work.

John

 

[jimi43]

I have tried all sorts of methods to make MDF edges presentable and the best result so far is simply adding a thin hardwood edging strip. If you are going to paint it even softwood would do. Glue it on, clamped until it sets up...trim then paint.

With standard MDF use a sealing wash coat of diluted PVA or proprietary MDF sealer. Otherwise it will eat up gallons of paint!

Jim

 

[superunknown]

I always sand to 240 apply a 50/50 PVA then 240 when dry. Prime and paint as normal. Always looks fine.

 

[hunggaur]

hi folks many thansk for all the info i think i will play around and if the worst come to the worst build a soft wood face frame and them gule and pin this on before painting. will let you know hoy i get one

many many thansk

jon