MRMDF

[Gary Morris]

Hi
I'm going to make a house plaque for my nephew, made out of mrmdf. I've searched previous posts and would like to run this past you guys if I may please.

Cut the shape out.
Sand down with a fine grit 320.
Prime with Morrells High Build Primer, then cut back with a finer grit 400/600.
Spray with gloss, then cut back to de-nib with wet & dry. (used dry)
Sand with wet & dry, then apply a second coat, then lightly sand.
Apply AC lacquer (not sure what the AC stands for) lightly sand down and apply second coat.
Lightly sand then polish.

The choice of mrmdf is a trial, I want to try it out on my scroll saw for the first time, as my nephew had hinted he'd like a house plaque, I thought I could kill two birds with one stone. I've read on here mdf dust is hazardous to health so will be wearing my mask along with extraction.

Thank You
Gary

 

[marcros]

is this to go outside?

mrmdf is moisture resistant- ie for kitchens and bathrooms, but not waterproof. sorry if you already know this.

 

[carlb40]

For external use i would use either timber or WBP/ marine ply.

 

[Gary Morris]

thanks both, Marcos, I never considered it! (and no I didn't thanks )
I will re think and get some marine ply I think, thanks Carlb40

I can do some sort of indoor feature with the mrmdf

Gary

 

[Chrispy]

You could use if you can find any "Tricoya" MDF it is true exterior MDF and paints really well. but I think AC lacquer is not good out side as the UV in sun light will break it down unless it made specially for that purpose.

 

[carlb40]

Marine ply is expensive, WBP is a bit more reasonable in price. If it painted the way you mentioned in your OP then it will be more than fine.
I got my sheet of wbp from mahoney's in sheldon for £30 inc vat for the 18mm ply. I think darlaston builders merchants in kitts green charge £25 inc vat for the same sheet.

 

[Graham Orm]

Shouldn't need to sand mdf initially. You will only detract from the surface as it is already extremely smooth. Also mdf tends to deteriorate and become 'fury' like cardboard would if you try to sand it. It gives a superb finish when painted without preparation other than dusting and tacking. (Tacking; wiping down with a cloth dampened with a thinning agent sympathetic to the paint that you are using to collect any surface dust). Tacking down should be done between coats after any sanding.
As said before, mdf is not suitable for exterior use.

 

[Phil Pascoe]

Make sure that you seal the edges of WBP before painting - otherwise it'll delaminate.

 

[Gary Morris]

Thanks guys, points noted (transfered to word for recollection) I'll take a drive out to Sheldon, and try Mahoney's.

thanks again
Gary

 

[Random Orbital Bob]

I agree with the use of WBP ply over marine for sake of cost. I've used loads of WBP painted for bird boxes and the oldest has been outside for 15 years now. I reprint every now n then