Bondo, Mixing Bondo

Bondo, what is the secret to mixing Bondo? The secret is in the thumbnail and it isn't what you think it is. If you guessed it let me know in the comments if you guessed it before watching the video!

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[tachyoncgi]

Thank you for being concise and to the point!

[MattInWA]

Awesome, thanks for the video. Getting ready to do a speaker enclosure out of MDF and I've never used body filler before.

[kolankprof]

Great Tips! Just what I was looking for! Thank You, Sir!

[OneCritic]

Is this actually a vid on "what not to do?" because I've seen multiple vids saying that you need one bead line across the bondo. Also the mixing like you're mixing a pot puts air bubbles into the bondo. You should use a figure eight mixing method.

[rg]

just got back from the store...why didn't they tell me I needed the spreader? For that matter, why isn't it included with the can?

[shepdogsd]

I would prefer 1 part hardener to to X parts Bondo to try in 10 mins, 1 part hardener to Y parts Bondo to dry in 20 mins. etc.

[devinmccloud]

Light pink, and it sets up in a few minutes. You barely have time to spread it smoothly. Definitely recommend the bondo spreaders. For $2, you can not go wrong. The hardener to bondo supply I disagree with. A one gallon can has a small tube of hardener. Buy a second tube. It takes more than you think to get a light shade of pink.
Does anyone use bondo on their gutters at the seems?

[jeffbguarino]

I found the density of the Bondo filler and it is 1.14. grams per ml. The density of the hardener is 1.2 grams per ml. I got these from the 3M safety data sheets.
So one fluid oz of filler is 29.57 ml and that is 33.71 grams. If you use 1.5% ratio then the hardener amount is .5 grams or .6 ml hardener. If you use the 2.5% ratio then you use .84 grams of hardener of about 1 ml.
So this large can of 3.18 kg has a bottle of 78 grams of hardener. 3.18 kg is 3.625 litres and 78 grams of hardener is 93.6 ml .
The volume ratio for the whole can is 93.6/3625 = 2.58 . So the % in the tube is 2.58. Many places say to use less 1.5 %.
So this gives a ball park range in ml. and now you know how much ml is a 3 inch strip. To calculate that from the can directions. A 3 inch circle 1/2 inch thick is 115.82 ml or about 4 fluid oz. 115.82 ml filler is 132. grams and 2.58% of that is 3.406 grams of hardener. 3.4 grams of hardener is 3.4 /1.2 = 2.83 ml.

The can could have just told you this. 2.83 ml hardener for the 3 inch circle that is 1/2 inch thick. So that is the starting point and you could use less hardener and find out how long the working time is, down to 1% or so. I have a lot of these little pneumatic push tubes that I can fill and measure exactly. Get them for ink cartridge refiling etc.
I am going to try a 1% mixture and see how many minutes work time and completely harden time I get. Some places say you use more hardener in cold weather and that the filler get hard due to heat produced in the mix.

[savannahtraderful]

I add a line of hardner the width of the blob of bondo. Seems to work but not much working time for the mix i use. The bondo I have came with blue hardner. So much for matching to a pink or tan spreader with the light blue color after mixing.

[relent]

Just grabbed some BONDO for a quick project, only used it a couple times with some decent results. I didn’t know this about the spatula color though. I’m sure it’s pretty common knowledge for someone who works with it often…but good to know for a beginner!

[barwithm]

Do you need to use the whole can at once? If not, how long can we keep it if we haven't mixed in the hardener?

[tyrotrainer]

Just done a repair with similar. Cardboard is messy and absorbs.... I used a smooth old kitchen tile, dead easy to mix and clean for reuse. I also use flat candy sticks for small amounts, throw em away after use.

[rencleavus]

I always mix it on a piece of aluminum flashing, it's nonabsorbent. If you have none, any lumber yard sells step flashing precut to 5 x 7 or 6x 8 for cheap.

[iancowan]

Can't remember who to give the credit to, but a trick i was taught was to use those wooden stur sticks and mixing batches in a small paper or plastic cup... at least with my old hands - easier for me! Fast clean up too!

[paulguilfoil]

You mentioned four or five times that the bondo will set up “very quickly”. But you NEVER told us what that means. How quick is that?

[garykay]

my bondo didn't have a spreader. someone stole it. that's what happens when you live in south florida. thanks for the video.

[timbartley]

Yes but one thing cardboard a no. No. Due to taken absorbed into cardboard

[sr]

My Bondo always comes with blue hardener and the spatulas are yellow or like in this video 😂

[fandechavalones]

its smells really bad do i need a mask ?

[Donnelly]

Mixing on cardboard isnt any good dies contamnate your filler u mix it the wrong way putting air into it and to much hardner for that amount of filler😮😂