It's too soft!
THere are great auto body putties that work well with MDF but I would not use drywall compound even if it was all that I had. It is much to soft. Will eventually break off and you will be sorry that you did it. Get a good ployester scratch filler. One that has to be used with a hardener. Canadian Tire has the stuff. Don't use the red stuff that comes from a tube. It just doesn't work that well except for very thin filling. Basically only for scratches and little dings.
Mark
Cabinetmaker at large.
THere are great auto body putties that work well with MDF but I would not use drywall compound even if it was all that I had. It is much to soft. Will eventually break off and you will be sorry that you did it. Get a good ployester scratch filler. One that has to be used with a hardener. Canadian Tire has the stuff. Don't use the red stuff that comes from a tube. It just doesn't work that well except for very thin filling. Basically only for scratches and little dings.
Mark
Cabinetmaker at large.
I do not think that is a good idea with dry wall compound, they are not strong enough.
I have use liquid nail apply to the edges using a 1 inch spreader/scraper to good effect. Just scrape off extra before it is set and they can be sand well and get smooth too. In fact I have used it to the MDF main surface using a 4 inch spreader to scrape on the surfaces, as MDF absorb it well just a very very thin layer of liquid nail left on it to really seal the MDF before painting. Work fast like plastering the drywalls.
The Butcher
I have use liquid nail apply to the edges using a 1 inch spreader/scraper to good effect. Just scrape off extra before it is set and they can be sand well and get smooth too. In fact I have used it to the MDF main surface using a 4 inch spreader to scrape on the surfaces, as MDF absorb it well just a very very thin layer of liquid nail left on it to really seal the MDF before painting. Work fast like plastering the drywalls.
The Butcher
Dry wall compound is not good to fill in cracks or, even worse, to build up a corner or edge if you'ce cut it wrong. I have had good results using dry wall compund to fill in the pourous cut edges of MDF. It won't help to seal the ends as the dry wall compund will let the MDF below it suck the paint right through it. What I have done is first seal the edge with a 50/50 mixture of carpenter's glue and water. Let dry then put a little bit of thin joint compound (kind watery is OK) on the edge with you finger. Sand it down with fine sand paper - after sandiong you should see MDF with just a light haze of compound in the pores. After this apply primer and paint.
Banned
Joined 2002
Bondo is not a surfacing putty!
Bondo can be used for really big goofups or making cool curved work. But it definitely is difficult to sand. The stuff that I am telling you about is made to be sanded. It feathers out to a nice edge. The scratch and filler putty that IS HARDENED WITH A CATALYST is more than durable enough.
P.S.
Liquid nails is a soft glue. I think acrylic or latex based. Not something that I would put paint or heaven forbid laquer. The glue ides works in a pinch but is much harder to make nice and smooth.
MArk
Bondo can be used for really big goofups or making cool curved work. But it definitely is difficult to sand. The stuff that I am telling you about is made to be sanded. It feathers out to a nice edge. The scratch and filler putty that IS HARDENED WITH A CATALYST is more than durable enough.
P.S.
Liquid nails is a soft glue. I think acrylic or latex based. Not something that I would put paint or heaven forbid laquer. The glue ides works in a pinch but is much harder to make nice and smooth.
MArk
There are many ways to seal mdf edges.
A. Diluted yellow wood glue with water, 50/50 mix.
B. Generic Bondo body filler works.
http://www.bondo-online.com/catalog_item.asp?itemNbr=176
[Comes with cream hardener.]
C. Minwax sanding sealer.
http://www.minwax.com/products/woodprep/sand-seal.cfm
D. BIN primer
http://www.zinsser.com/product_detail.asp?ProductID=10
If you want to seal the MDF but not the edge, then I would
use the Bin primer or the sanding sealer, but not Bondo
or diluted wood glue.
A. Diluted yellow wood glue with water, 50/50 mix.
B. Generic Bondo body filler works.
http://www.bondo-online.com/catalog_item.asp?itemNbr=176
[Comes with cream hardener.]
C. Minwax sanding sealer.
http://www.minwax.com/products/woodprep/sand-seal.cfm
D. BIN primer
http://www.zinsser.com/product_detail.asp?ProductID=10
If you want to seal the MDF but not the edge, then I would
use the Bin primer or the sanding sealer, but not Bondo
or diluted wood glue.
Bondo will work but you have to stay on top of it as it cures. Get the shape close and let it set up some. When it is starting to gel, cut out big chunks. When it is starting to get hard, file down the rougher spots. Done properly, not much sanding is required.
What you have to sand, though, will take some elbow grease.
What you have to sand, though, will take some elbow grease.
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