The guy who I've been working with uses fiberglass resin, the kind you buy with matting and the little drippy hardener tube. Don't use any of the hardener, just the resin (maybe that's what you're referring to as "poly resin"?). That's all I've ever heard of used to thin out filler. Also, if you have some old stuff and you let it sit on a shelf for a while, the solids sink to the bottom and the creamy goodness rises to the top, so you can scoop off some of the thinner stuff from the top of an old can.
That's about the best. The Evercoat glaze coat is an easy sanding nice viscosity in the first place, and you can blend it with body filler like their Rage and get the consistency you need and still have easy sanding. Thinning with too much resin alone could make the end result more brittle and harder to sand. It's easier to get a nicer sanding and more flexible mixture by blending the glaze coat and body filler. overspray
I experimented with thinning filler to spray it, using it like a two part high build primer. I was able to thin it out using acetone. Look on the side of the can and find the chemicals it made of.
I wouldn't be messing with "thinning" bondo by mixing something else in there. I'm not sure what the problem is you are trying to correct. if you need a "light thin wipe of plastic" push harder with your spreader..
Feather-Fill has been around for a million years and isn't that expensive if you want a sprayable polyester resin filler.
I use Ever Coat "Plastik Honey" #1249 in my Rage to help it flow out better. All it is, is the polyester resin that it already has in it. It really helps with pinholes and slows the dry time a bit on a humid day.
Open any body shop supply catalog and there has to be about 50 different glaze type compounds. Anything from easy flow to almost as hard as regular. With that said why in the world would you go and be a chemist and start mixing different things together. If you can't spread a 2 part glazing putty to a thin layer you are doing something wrong. Try a rubber squegee. Don't blame the plastic when you have a problem later on down the road. Cost of can of bondo and acetone to make the home made so called sprayable filler vs just buying Featherfil??? Come on are you serious?? These are the exact reason why bondo has such a bad name.
I put a lil fiberglass resin in my body filler to thin it learned it at a body shop and makes spreading it easier to work with but I usually do it on a final coat I was told by old timers thats how they use to do it before glazecoat was invented
Do NOT use acetone to thin down polyester resin based fillers!! It will compromise the properties of the cured system. If you absolutely have to thin it use a sprayable polyester filler, straight polyester resin, or styrene monomer (in that order) Besides possibly affecting the sandability, these are also going to give more shrink to the system too ( but are at least likely to be compatible) Barry
Slick Sand. It's a more user-friendly version of Featherfill. It's a slower build and sands easier...waaaaayyy easier. If you don't get greedy with it shrinking is no concern. Good luck.
cant you just use a couple of coats of high build primer then flat it back, that will more than fill in sanding scratches.
I have actually started using Marson Platinum filler when I need filler. It is made by Bondo, and is about 2/3 the viscocity of regular bondo. When I need it thinner, I put it in my paint shaker for about 2-3 minutes. This ensures it is mixed well and also thins it down because of the heat generated. Any time you use the "skim" that has settled or adding another chemical to thin it, you compromise the chemical make up and cause potential problems down the road. If I need thinner material than that, I use "Icing" catalyzed glazing compound, it has enough for the in between projects, but is not quite as thick as regular putty.
Yeah, old thread, and here's a good reason why I search them. Needed to do some minor repair work today. My auto body class is closed for the shelter order so I couldn't get some killer Rage Gold like I normally use. Didn't want to chance a trip to the auto parts, supposed to be essential travel only and I've made it this far without getting sick. Had a small can of Bondo brand filler on the shelf but it was too thick, not lumpy, just thick. I was about to dump acetone in it when I though I'd better check that out first and found this thread. Never would have thought of fiberglass resin, had a pint of that too. Man, worked like a treat, nice and creamy, dried and sanded as normal.
Styrene is the thinner in body filler. It is the part that evaporates off to harden the filler in addition to the MEK hardener which is a radical to create heat. Styrene to polyester body filler is like paint thinner is to paint.
Good post @ Blowby I too have been miserably miserly with materials and supplies - writing down notes of things to get after it safe to go out - now where did I leave my pad Stay safe everyone Sent from my iPhone using H.A.M.B.
Polyester resin is thinned to viscosity by liquid styrene. Fresh resin will thin old filler to a point because of the styrene in it . The styrene is what has evaporated over time from the filler. Fiberglass resin, silica and styrene are what body filler is made of. The styrene is the thinner and is what needs replaced. It will take less styrene to bring it back faster than adding more resin which is thinned with styrene.
It is NOT a good idea to use fiberglass resin to thin fillers. Thy are not the same as the resins used in filler hence the need for different types of hardeners to catalyze. Using resin can result in shrinking down the road because BPO style hardeners that come with body fillers are not strong enough to fully harden fiberglass resin. There are products specifically designed to do this (Plastic Honey, Supercharger). The "I've done it many times without problems" camp is the same as it is with anything else used improperly it great when it works but you are going to wish you hadn't done it if you get your painted car out into the sun and the areas where you have used thinned filler start to sink.
I always put bondo in my rotary paint mixer for 5-10 mins depending on how long its been on the shelf. It comes out very creamy and easy to spread. Also I store my bondo upside down so the resin will go to the bottom of the can stored up side down. To use it I put it in the mixer as stated and then it is smooth an ready to spread easy.. Using a rotary mixer eliminates air bubbles. just sayin' brasscarguy
I have been in the fiberglass industry for over thirty years. Have used both BPO (Benzoil Peroxide) and MEK ( Methyl Ethyl Ketone) hardened polyester. My information has came from Alpha Owens Corning, Ashland chemical companies and a direct line into the Corvette engineering department. I may be wrong but with my limited expertise on this subject, I think these are a pretty good source. I usually will stand down when I am not very sure of a subject but this has consumed a great deal of my life. I will stick with the done it for years camp.
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