So you know how often a coat of primer can bring out a defect not quite that detectable by eye on naked wood?
Very time consuming correction for what it's worth if you ask me.
I was shown to sand down the product and shove bondo in there. A little problematic because bondo does not adhere to paint, and you can't quite sand paint out of a crack. so by the time you sand down the bondo I noticed that you often rip the bondo right out of the crack. I sometimes just skim it and sand smooth layer with 150 grit. But that still sometimes ends up with bondo being ripped out of the crack.
Now what if I used wood glue? Fill it, scrap off excess with putty knife then sand once dry. Nice viscous liquide that would fill the crack entirely just and stay there... And doesn;t require 3m mask to apply.
Any reason not to do this? I thought I;d ask first because I don't want to just try this thinking I'm oh so smart and end up getting returns down the line because I'm missing something.
The problem is adhesion. Inside of the crack it is almost impossible to get down to clean wood. Spackle will work if you can get paid quickly and don't want to do more work for them. Glue might work for a hair line crack but getting it deeply enough in to hold is difficult. Mask the area, put a bead of glue on the crack and use an air nozzle to gently force the glue into the crack. If the crack is a bit bigger follow with some sanding dust mixed with glue. There don't seem to be any perfect solutions other than ripping and re-gluing.
Okay so I've since been going with the glue and pressing it down with a putty knife to ram it in there. Then I;ve been sanding before it's completely set to get a bit of sawdust in the mix as suggested. So far, so good. Faster then anything else I've tried so far, and it's been sticking. Feels like hackery, but working good!
On another note--I've been also using woodglue for mdf profiles. I was chatting up the painter who said she has a hard time painting the mdf end grain of profiles --eats an obscene amount of paint. So she suggested smearing it with glue and wiping off the access. Going good so far.
I use super glue for this sort of repair. I'd spray some activate onto the surface and into the crack then apply glue and use a putty knife to force it into the crack. it sets up quick, a larger defect I use more super glue.
I have $60k kitchens that are 15 years old that I used Muralo spackle on. Many of those are waterborne. They are all still perfect. No cracking in beaded faceframes and shop made doors with applied miter moldings. This was all soft maple, birch ply, and a bit of mdf for door panels.
Like I said a true gift. We stopped using wood filler or bondo for anything less than a screw hole. Sand 150 grit, prime, spackle, sand 240, paint. No filling before the primer. The spackle blends perfectly into the prime coat. No need to reprime over the spackle.
Skip the glue on MDF. Try to use ultra refined MDF for a start it is less porous. Sand the end grain of the mdf with 240 grit. Brush BIN shellac or a catalyzed solvent primer on the end grain. Sand it with 320 grit. It will be as smooth as the face and no longer porous. We have done thousands of raised panels in mdf.
1. shape the profile
2. sand mdf end grain only 240 grit
3. spot prime end grain BIN or Clawlock
4. sand mdf end grain primer 320
5. spray the entire panel with primer.
6. sand the entire panel 240 grit
7. 1st topcoat, 320 grit, 2nd topcoat
1. use a decent amount of glue
2. sand the frames 150 grit
3. prime frames
4. fill all of the dark spots with Muralo Spackle
5. sand the primer and spackle 240 grit
6. 1st topcoat, 320 grit, 2nd topcoat
The old school way was to build your frames putty every defect you see(which is not many). Then prime it and then putty all of the spots you missed with a product inferior to spackle. Then you sand the putty off and generally have to reprime it.
Alot of wasted time. We've all heard of using sheetrock compound, bondo, and glue size. To solve the "mdf problem" the reality is all you need a fast drying sealer that hardens in the mdf end grain. Shellac and catalyzed primer fit that bill.
Told the painter today about your spackle. Her eyes got all wide and happy--she's got a can of it that she uses to fix mistakes when no one else is around. She's been telling people to use it for years. Set me off with the can and I'm widely impressed.
Will try the profile trick next time. Thanks for the very specific instructions, I love that.
The old school method is frustrating and time consuming. Happy to see other people nerd out on adhesives. Proper adhesives are most definitely your friend.
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