Anyone experienced with using Bondo?

[Jim Dalton]

I was told by a master painter that he always used Bondo to fill nail holes and cracks before painting work which was to be outdoors. I tried a bit and have some questions.


What can you use to thin Bondo?
What can you use to retard the setting time?
Many thanks,

Jim Dalton

[Doug Shepard]

It's been about 30 years since I've had any serious experience with Bondo. My grandpa was a whiz with the stuff and helped me patch up the first car I ever owned. My memory is fuzzy, but I think I remember him using lacquer thinner and retarder with Bondo. Hopefully someone with more experience will chime in.

[Phil Winn]

I emailed you some posts on thinning Bondo----I have never used the stuff, but did a search using Google---bondo and thinner.
Phil

[jack duren]

just use less hardener. it will give you more open time. but....how much hardener depends on experience. too little may take to long to harden, too much youll never get the product used before it sets.....jack

[Howard Acheson]

I've used lots of Polyester Body Filler over the years.

Why do you want to thin it?

You can slow up the cure time by using less hardener. Also, keep it cool--I sometimes put my container in ice water to slow it down a little. But, one of the benefits of using Bondo is that it does cure fast letting you get to sanding and finishing much faster than using most other products. If you have lots to do, it's best to just mix it up in small batches as you go along.

[Frank Hagan]

Ditto on the "use less hardener" solution to longer open time with the stuff. If you are doing larger areas, you can shape it easily with a Surform shaper / rasp when it is in the rubbery, cheese-like stage. Much easier than shaping it once it gets rock hard.

A while back, FWW had an article on using it for things like bedding bolts in MDF, which struck me as a kind of anti-FWW article. But the author was a pro who used it for that type of thing on furniture, etc.

The standard Bondo is not waterproof, so it must be painted or sealed with something else waterproof if it will be exposed ... I used epoxy over it on a home built boat. Not everything sticks to it, but epoxy will.

[Phil Phelps]

I use a product that is thinner than regular Bondo called Icing. Different brands of it. Check it out at the automotive finish store. Don't mix more than you can handle for each job. As it begins to set, use a surf former to scrape away the excess before it completely hardens. Don't froget to prime.

[Carl Eyman]

I hesitate to advise with all these experts around, but for what it is worth here's is my experience. A group of friends and I undertook to restrore a 74 ft. oyster boat to a pleasure craft some 17 years ago. Since this craft was 60 years old when we started, you may surmise there were some obstacles.

When structural concerns were not an issue, we thought bondo might be a solution. It is much used by commercial fishermen here abouts. In short, if the patch is big (more than 4 sq in) forget it. we tried reinforcing the patch with brads driven into the wood, etc., etc. but the patch seemed to peel off anyway. If the patch was "keyed" in, that is the bottom of the hole was bigger than the top, it was better. But the overall experience was that the wood continued to rot beyond the boundaries of the patch. If rot is not your problem. then the results are likely to be much different.

Oh, by the way, I think the fishermen use bondo just as they are fixing their boat up for sale.

[Bob Johnson2]

Don't know how thin you want it or why but if you use a new or newer can of bondo (there are better brands then "bondo" around, like 3m lightweight) and you mix it well with the hardner at roughly room temp it should be good and workable, kind of like ready made dry wall compound. If it's too cold or old it doesn't seem to get the creamy consistency that makes it easy to work and be pretty much air bubble free. I use about an inch of hardner to about an egg size pile of the resin, you could maybe go half that much hardner but be careful, you can use too little and it'll never harden. As others said, you can rough shape it with a shurform or even a pocket knife just before it hardens up, It'll feel kind of rubbery but your fingers won't smear it, someone mentioned cheesy which is a good description of it. You can also very rough sand it (40 or 60 grit) at this stage although it fills the sand paper. I do all the close/finish sanding after it's hardened completely. As it's only for nail holes and such I'd put it on like putty and scrape it flat right away, if needed use a thin second coat in 30 minutes after it's set up.

[Frank Hagan]

I hesitate to advise with all these experts around, but for what it is worth here's is my experience. A group of friends and I undertook to restrore a 74 ft. oyster boat to a pleasure craft some 17 years ago. Since this craft was 60 years old when we started, you may surmise there were some obstacles.

When structural concerns were not an issue, we thought bondo might be a solution. It is much used by commercial fishermen here abouts. In short, if the patch is big (more than 4 sq in) forget it. we tried reinforcing the patch with brads driven into the wood, etc., etc. but the patch seemed to peel off anyway. If the patch was "keyed" in, that is the bottom of the hole was bigger than the top, it was better. But the overall experience was that the wood continued to rot beyond the boundaries of the patch. If rot is not your problem. then the results are likely to be much different.

Oh, by the way, I think the fishermen use bondo just as they are fixing their boat up for sale.

I have heard that the problem is with the fillers used in the polyester resin ... talc, or some other material that will wick up water. I know one boat designer who uses Bondo a lot in the prototype stage, and he said they get about 30 - 45 minutes into their float test before the Bondo starts to flake off. But by then they know what they need to know, and the stuff is cheap.

But for filling nail holes? Probably OK, if its painted. I like epoxy better, as its more water resistant and REALLY sticks to most things.

[Hal Flynt]

You may want to visit an automotive paint supplier and see what they have in different fillers. Some won't shrink and are water resistant others waterproof. Others are thinner than joint compound. 3M makes a line of glazing putties used to fill the pin holes in the "bondo". I use them from time to time to fill nail holes. They are lacquer based and dry very quickly, sand extremely smooth.

[Richard Wolf]

I like to use Minwax high preformance wood filler. It is bondo, in a wood tone and I would guess it's 3 times the price. I just think it looks much more professional when used in the field.

Richard