Autobody filler/compound in woodworking?
billstuckey
| Posted in Construction Techniques on
I’m curious if anyone has ever used autobody filler in woodworking to fill large voids or gaps, that will later be painted.
I have a situation where i need to fill an area that is about 6″ x 14″ by about 2mm deep. I would normally use wood and sand it smooth, however it’s on an inside (concave curve) and I would never be able to bend a piece to fit the exact curve. It’s part of some interior architectural woodwork that has been damaged.
Using drywall compound or spackle would be to brittle to withstand the seasonal movement of the underlying wood. I’m wondering if auto body filler may just be the ticket here, since I’m sure it’s very durable and built for some movement.
Any help would be appreciated.
Thanks.
Bill
Replies
The Minwax Hi-Performance Wood Filler is essentially auto body filler.
So real body putty should be no problem.
Bill -
I had a problem with some exterior wood a while back and a few guys said they used it successfully, even outside. I didn't take that route, but did file it in my bag of tricks for possible future use.
Don K.
EJG Homes Renovations - New Construction - Rentals
been there, done that, it works. This from an origional hill billy.
2 mm is not very deep for such a large area.
I think I would rough up the wood and maybe drill some holes to give the filler some bite.
I would probably suggest an epoxy from Albatron. They make a kit with 2 different 2 part epoxies one a paste the other set is liquid and you can mix the 2 sets so that you get the consistancy you feel spreads best.
The only problem with the epoxies is they take a good 24 hrs to set up fully.
The bondo can set up as fast as you want by the amount of hardener you mix in.
You could tack some screen down then bondo to give you more bite.Also note that you can't hammer or screw the bondo as it will crack.
ANDYSZ2
I MAY DISAGREE WITH WHAT YOUR SAYING BUT I WILL DEFEND TO THE DEATH YOUR RIGHT TO SAY IT.
Remodeler/Punchout
The abitron wood epox is the best out there for for wood restoration. I know some guys that use marine epoxies from West Systems. Bondo is made for a substrate that is not going to expand or contract like wood. Min wax is ok but nothing like the abitron products.
I used it to fill voids on window sills. Dig out the old softened wood and fill the void with the bondo. Sand smoth prime and paint, helped turn 60 year old window sills into looking like new.
One of the designers of small wooden boats - Stevenson, I think, called for the use of autobody filler to fill all of the imperfections on small plywood sailboats etc. over screwheads, nails etc. If it will live in an environment like that it should survive indoors.
Autobody compound is usually made up of a polyester resin and hardener combined with a talc filler. The only gotcha of using it outdoors is that the talc can absorb water, (of course wood absorbs water too). If is usually not recommended for marine use under water for that reason.
In marine areas they use a filler, not sure what it is made of that doesn't absorb water. Of course they are more expensive and then they also use the more expensive and stronger epoxy based resins.
West system and other marine suppliers offer fillers and epoxies separately which is nice because you can mix them to your desired consistency. In addition I have used 5 min epoxies with the fillers in the past for patching as well.
All of the that said, IMHO, Bondo, if painted will work just fine for most applications in home building.
We use it quite a bit in the custom millwork shop where I work. Filling voids from screws or chipped out ply to support laminates. Also as filler for nail holes and seams on some stain & lacquer work. On some dark stains on maple or oak where red is the predominate colour, it works (hides) better then normal wood filler. Of course, use the body filler with the red catalyst. It goes without saying, always make up a sample finish panel first.
Paul
Some people worry that bondo may not hold well as the wood expands and contracts. But I certainly have heard of a number of people using it.
You will not go wrong using the Abatron product however. It is designed for wood, including exterior applications.
I have often used auto body filler on yacht topsides to fill small imperfections, although I probably wouldn't use for your problem.
polyester resins don't adhere to wood very well, using body filler on screw heads and small cracks and dings works well but to fill an area 6" by 14" you may find the filler puckering and falling off.
Filling a large shallow area is a common occurrence in boatbuilding and repair, and there are several filler systems available to do this, look here:
http://www.jamestowndistributors.com/userportal/search_subCategory.do?categoryName=Fairing%20Compounds%20and%20Repair%20Putties&categoryId=528&refine=1&page=GRID&history=v5k4c430%7Ctop_category%7Cpage%7EGRID%5EcategoryName%7EEpoxy%2Band%2BAdhesives%5EcategoryId%7E203%400c6asjq2%7Cother%7Crefine%7E1%5Epage%7EGRID%5EcategoryName%7EFairing%2BCompounds%2Band%2BRepair%2BPutties%5EcategoryId%7E528%40ner5an91%7Cother%7CrefineType%7E1%5ErefineValue%7EEpoxy%5ErefineName%7EComposition%5Erefine%7E1%5Epage%7EGRID%40fgkksv0m%7Cother%7CrefineValue%7EFairing%2BCompound%5Erefine%7E1%5ErefineType%7E1%5ErefineName%7EEpoxy%2BType%5Epage%7EGRID
I have used bondo dozens of times on millwork, and it works great (although I'm always a bit embarrased to admit it). The filler adheres exceptionally well to wood in my experience. The only problem is with new work where the wood might contract a bit, while the bondo doesn't. This results in a slightly raised area. There was an article a couple of years ago in fine woodworking where a guy was using bondo to smooth cabriole legs that had a black laquer finish. Sands smooth as glass.
I have used Bondo type auto body filler products, but my experience has not been very good.
The stuff that is specifically formulated to use with wood seems to expand and contract in concert with the wood substrate, and therefore does not separate from the wood -- which has been my experience (sometimes) with the auto body filler. That is, it doesn't seem to do so good if it is fully exposed to the weather -- sun, rain, snow, etc.
The two brands of wood epoxy I have used with best results are Abatron (my preference) or something called PC Reddy (from my local paint store). Both are great, but they are substantially more expensive than auto body filler.
What to do? If money is no object use a wood epoxy -- or if the repair is highly visible. Otherwise, auto body filler will suffice. Curiously, some of the auto body fillers are not waterproof, so be sure to get one that is.
********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
I gave up on bondo type polyester fillers. The short strand fiberglass fillers work some better. But epoxy fillers are the only ones I have had luck with over time.
I thought I'd add my two cents in, I'm a pattern maker at a foundry. We use auto body filler all the time to make small repairs in the molds. It holds up very well in the conditions it's subjected to.
I think auto body fillers can work for any number of applications. The problem seems to be when you use them with wood, and then subject them to weather extremes. When I make TS cove moldings I often use auto body filler to make a mold of the profile, and then wrap sandpaper around it for final smoothing. So I can certainly see how it would work just fine in your case.********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
>When I make TS cove moldings I often use auto body filler to make a mold of the profile, and then wrap sandpaper around it for final smoothing.
That is a great idea. I have a bunch of fluted casing to paint strip and sand. The molded sanding block is great.
What do you put between the bondo and wood to get it to release? A shot of cooking spray?
splat
Not trying to bud in on Nikki but I do the same thing for a sanding block.
I put a piece of waxpaper down then glob my bondo on it. I usually lift up on the ends just slightly so that the sanding block is just a tad bit tighter radiused then the actual cove, helps sand mo-better for me. It actually helps me get down into the deep part of the cove easier.
Another thing I do in that situation is make a simple wood handle and insert that into the bondo before it sets up, makes it easier to hold while sanding.
Doug
I do exactly the same thing that DougU does -- waxpaper, bend it up a bit before the bondo sets. I like the idea of setting a handle in the bondo; in the past, I've just carved out some finger grips along the sides so I could grip it a little better.********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
I use the Minwwax or Bondo Home Solutions varieties, I think the formulations are tweaked a bit to accout for the Ph of wood.
The most important step is to clean out all the dust from the area to be filled or the patch will not bond to the substrate.
Jim
The awful thing is that beauty is mysterious as well as terrible. God and the devil are fighting there, and the battlefield is the heart of man.
- Fyodor Dostoyevski
For interior stuff, Durhams Rock Hard Water putty applied in say two fills, works real well. I also use titebond glue as the liquid instead of water if it is getting painted.
Mix any thickness ya want and no fumes to stink up the place.
Spheramid Enterprises Architectural Woodworks
Damm, I miss that stuff
That's interesting.
I never thought of mixing Durham's with glue.
Why for painting?
Durhams takes stain sorta kinda, but if mixed w/glue it wont. For painting the glue is acting like a primer and sands smoother and blends in better than a splotch that shows thru the paint.
Spheramid Enterprises Architectural Woodworks
Damm, I miss that stuff
Thanks
I've also used regular auto Bondo to patch small holes in very expansive aluminum siding. It worked fine.
D&L
since Rock Hard is mixed with water maybe water based dyes would work
Ya, that works.
Speaking of stains and dyes and fillers, Bondo can be tinted w/ oil stains or oil paints too.
Spheramid Enterprises Architectural Woodworks
Damm, I miss that stuff
I've never used Durhams Rock Hard Water putty, but I'm always tempted to try new stuff. I'll have to give it a try if the cure time is reasonably fast. What was this stuff originally intended for anyway? What are it's strengths/weaknesses?
-Don
It is intended for filling wood. Strengths? Sandable, drillable, stainable( to an extent) , easy mix with water, sets fast and hard. No fumes. Tintable. Cheap. Long shelf life (unmixed).
Weaknesses..sets HARD. Some shrinkage. does not take stain REAL well ( nuthing but spackle does IMHO).
I love the stuff. Useually mix to about Pnut Butter consistancy and work fairly fast.
Try it. Cheap experiment.
Spheramid Enterprises Architectural Woodworks
Damm, I miss that stuff
Thanks. I'll give it a try.
-Don
Durhams Rock Hard has been a staple on my shelf forever. Interior and exterior uses abound.
I usually make a "dam" with blue tape around the area to be filled. You can then knife it smooth with the tape to overfill the area a bit. Remove the tape BEFORE the putty sets and you have a nice area for sanding that is only slightly higher than the substrate. The thinner layer around the patch is MUCH easier to sand smooth.
TIP: Save your egg cartons and use the egg sections to mix small batches. Free and you get 12 doses that will fill most knot holes.Troy Sprout
"Don't forget the screws"
For interior use I expect the Bondo would work well for this application. Even a one part filler would probably do the job.
I think epoxy would be overkill for an interior situation with no structural aspect to it.
The two part Bondo works well and it's also nice to have the accompanying glazing putty around to fill small voids and hairline cracks. Glazing putty is used straight from a squeeze tube and because there is no air in the container it lasts forever.
For holes deeper than yours consider adding nails in a cross hatch pattern for extra purchase by the Bondo.
As long as the wood is in good shape, small fills with Bondo work very well. For larger fills, or damaged wood, I'll generally use the Abatron Liquid Wood as a primer. Several coats, until the area to be filled feels hard and "plastic-y", and has a sheen to it. Then the body putty works well.
If you're trying to fill rotted wood, the Abatron stuff is the only way to go, but their epoxy filler is harder to work with and expensive. I'll prime with the Liquid Wood, fill 90% with their epoxy, then topcoat with Bondo.
Been there, done that. Works well for repair work because it's so easy to shape and sand. Works great to fill nail holes and blend in resinart flexible moldings too.
Bondo is fine for some applications but it's not formulated for wood. I have used it on interior and exterior and find that the wood movement makes the fill pop out, or over the course of a year or so you can always see the separation of the two materials.
I do what Sphere does and that is mix glues in with fillers. I even make my own with epoxy or aliphitic resin glues and fine wood dust that has been collected from my orbital sander. Bondo doesn't stick as well, but it does sand out smoothly.
You can mix in universal colors or powder pigments with Bondo or Water Putty for the desired color.
I have had good luck with the WoodEpox system, also the West System is good for exterior wood.
I'm a bondo man, but, Durabond is another interior option, Keep an eye on it and you can shave it just before it hardens.
I can't belive the Durham Rock Hard repeat users...shaping/sanding that stuff when it's dry is an exercise in futility...it's not even in my top 20 options<G>