Using Bondo Mix Question

NavMidn

Active Member
RPF PREMIUM MEMBER
This is a real newbie question, but I haven't been able to find an answer to it: I'm trying to use bondo on a small scale (prop stuff) but the mixing instructions that come with it are directed at volumes used for car body work. I was wondering if anyone could give me advice on what sizes to use as a volume reference when mixing the putty with the hardener e.g. a golf ball sized amount with a 3/4inch strip of hardener? I just can't seem to get a mix right so far in a small enough amount that i'm not wasting a lot more than I'm using. ALso, I think it does but just to make sure, does Bondo work well on styrene?

Many thanks,
John
 

bondoking

Sr Member
What I usually do is , no matter what portion of bondo I use ,I make an x across it with the hardener. than mix---it hasnt failed me yet... and bondo sticks to everything.
 

Stormleader

Well-Known Member
I don't think there's any "right" answer to this. I think you're going to end up wasting a lot either way- unless you know EXACTLY the amount you need and EXACTLY how much working time it will take to apply it.

I usually just mix by color, the more red it is, the faster it's going to kick, and mix more than I know I need. It's hard to describe, I go for a light pink or salmon color and if I think I need more catalyst, I squirt another little blob on there and mix.

Not exactly the most scientific approach, but it works for me. :lol
 

NavMidn

Active Member
RPF PREMIUM MEMBER
Thanks guys, that pretty much answers my question. It sounds like bondo is pretty flexible as far as mixing goes so trial and error won't lead to any catastrophes. And the light salmon color is what i've been getting. I appreciate the help.

Thanks,
John
 

DL 44 Blaster

Sr Member
3/4 bondo to 1/4 hardener.....in any ratio be it small or large :D

I've mixed up small enough amounts to fit on a tablespoon,so it's a great ratio to use....I think it's even on the can if I'm not mistaken.

Steve
 

Rick Hanson

Sr Member
RPF PREMIUM MEMBER
Fun fact: the color of the little Bondo-brand applicator/trowel thingies is exactly the color that your Bondo should be when properly mixed. :)
 

gavidoc

Well-Known Member
After using it a while you'll just be able to tell if you know what I mean.

What others have said. Light pink is a good ratio.

The more hardner you add, the quicker it sets, but the more it shrinks. Even though it says it won't shrink, it will after a few days if you mix in too much hardner.
 

propcollector

Sr Member
RPF PREMIUM MEMBER
Originally posted by gavidoc@Jan 7 2006, 03:49 AM
After using it a while you'll just be able to tell if you know what I mean.

What others have said. Light pink is a good ratio.

The more hardner you add, the quicker it sets, but the more it shrinks. Even though it says it won't shrink, it will after a few days if you mix in too much hardner.
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The bondo is grey and hardner is red,The lighter pink that the bondo is after mixing the longer it will take for it to harden so if you want it to harden fast the color will be darker. I do a lite pink so as to work with it longer.

Mark
 

imurme

Active Member
Now I know this thread is WAY old but I thought it should be added that the proper mixing ratio of Bondo to hardener is 50:1 by weight. (according to the Bondo website)

FYI
 

DtailedREPLICAS

Active Member
Indeed imurme. VERY old thread. But timeless information.

Whoever said '3/4 bondo to 1/4 hardener' must be constantly out of hardener though. That kind of ration would set in 2 minutes on a hot day here in Aus.

Also, never put anything solvent based on polystyrene.
How do you know its solvent based? Read the can and see what's in it, or alternatively, smell it. If it smells bad, its probably solvent based. It will turn your polystyrene into goop!
Seal it first with an acrylic paint or primer, or a few coats of watered down PVA (elmers) glue.

Always test EVERYTHING on a sample before you ruin hours of work!
 
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