How To: Use Dry Ice to Remove Tar Insulation

[SuperDave]

One of the ugliest jobs I've done while stripping down an old 240Z has been removing the tar-like insulation that covers much of the interior floorboards and transmission tunnel. I have done it by using aircraft paint stripper, but this was a big mess. It softened up the tar, but made it flow into low spots. Once I had most of it removed with a paint scraper, I had to use a wire wheel and more paint stripper to get the last of it off. Some have suggested using heat, but I'd think this would also be a mess. There must be a better way.

Actually, I found that with no chemicals at all, some of the insulation will come off quite easily. Just get the corner of a paint scraper under it and it flakes right up and breaks off. That's the good news. The bad news is that, unfortunately, these pieces come off easily because of what's underneath--rust! The insulation that covers clean metal doesn't want to budge.

A few years ago, a fellow racer had said that dry ice was the best way to clean off this insulation. I saw it mentioned a couple of other places on the internet, but I couldn't find any articles about it. Armed with just a few instructions of how to do it, I decided to give it a try. I would try to use dry ice to remove the insulation tar in the rear hatch/ trunk area of the old 240Z.

Getting the dry ice was easier than I thought. My local Kroger stocks it for 99-cents a pound. They broke open a ten pound bag to sell me 5 pounds. I brought it home and tried to break it up into as small chunks as I could. Then I simply spread it on top of the insulation tar. All the areas I treated were level. I don't know what is the best way to apply the dry ice to vertical areas like a transmission tunnel.

I got a really good feeling about this process when, before I was finished spreading the dry ice, I could hear cracking sounds where the dry ice had been sitting for a few minutes. Due to the cold, the tar must have been shrinking faster than the metal and finally becoming separated from it! Once I had spread out the dry ice as best I could and broken it into as small chunks as seemed reasonable, I went inside to watch the finish of the Daytona 500 and to eat supper.

I came out about two hours later. All the dry ice had melted (had become CO2 gas and sunk invisibly to the floor and out of the garage). I started attacking with my paint scraper.

Now, with minimal effort, chucks of the insulation as big as 3-by-9-inchs broke right off. In just a couple of minutes I had removed almost all of the insulation tar.

The bad news is that I found some really nasty rusty areas that I wasn't aware of. But they will be fairly easily repaired. I'm glad I know about them.

I did not try one technique that I had read about elsewhere--to use a hammer to strike the insulation. It is supposed to just shatter like glass. I was afraid this would leave dents in the underlying metal. And, if I remember it correctly, you're supposed to strike it when it's still cold (and mine wasn't really dry-ice-cold when I tried to remove it).

I didn't get every bit of the insulation. I think there were some spots where I didn't spread the dry ice thoroughly enough, so I guess the insulation didn't get cold enough. So it looks like I'll go back in a few days and repeat the process on those spots.

This was an incredibly effective and simple process and I will highly recommend it to anyone who wants to remove this material from any type of vehicle. It didn't involve any nasty chemicals, and didn't leave anything to clean up. Obviously there are precautions to take--I used leather gloves to handle the ice. It gives off CO2 gas, so make sure you have some fresh air to breathe. Other precautions will usually be listed on the package of your dry ice.

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[e_racer1999]

good info!

[Bambikiller240]

Heat applied for a 1600W hairdryer, or other heat gun works well also. The concept is to apply enough heat to soften the tar-mat, not melt it. I tried to find Dry Ice, but I'd have had to drive to another town to get it, so the heat method was more convenient for me.

[TomoHawk]

Did you heat from the top, or from the back? It makes sense to me to heat the underside, so only a thin layer next to the metal softens and you have minimum cleanup after removal, and it doesn't all melt and flow into worse places.

[MikeW]

I used a heat gun as well. The idea is to just soften the whole thing up enough for it to peel up and not break into little pieces. It's not enough to melt it completely and it comes up easily with a plastic paint scraper.

[Bambikiller240]

I heated from the top, stating at an edge and moving inward. I liked the control I had to remove only what I wanted of the tar-mat. The tar-mat is not prone to melting (liquifying) unless you don't pay attention to what you are doing. As for "clean up", no matter what, you'll have to wipe the metal down to remove what I can only describe as a stain on the metal from the tar-mat. I spent about 2 hours total (including clean-up) to remove the mat from both driver and passenger floor pans (and about 3" up the tunnel on both sides).

[Victor Laury]

I'll try to find the link.... but.. One of the Roadster guy's did this with the "hit it while it's cold" method, and WOW! did it work. The whole floor was cleared with a single blow

[AChev]

I used a heat gun and paint scraper also. A tool that also came in very handy was a chisel meant for wood. I would heat up maye a 6" x 6" sectionand then using the chisel I would slide it beneath the tar paper and hit it with a hammer, that was very effective, it worked better than my paint scraper and screw drivers. When all was said and done it was not too bad. Although I would have especially preferred to use dry ice.

Work smarter not harder I always say

[EricB]

very cool - thanks for the write up

-e

[EScanlon]

Excellently written article and superb use of before / after pictures. Kudos SuperDave

When I removed mine, I was able to use the paint scraper method and a RUBBER mallet. The rubber mallet allowed me to strike the metal directly without deforming the metal from the strike. Since I was specifically addressing a "High-Curb" pan hit, the loss of the tar was an added bonus but noteworthy for this application.

2¢

Enrique

[SuperDave]

I used heat to remove the final bits of tar that the dry ice didn't get. I pointed a 500W light down at the section I wanted to remove, then did other tasks and came back in about five minutes. The tar was pliable and peeled up easily. But it didn't remove it as cleanly as the dry ice did. There were numerous little bits left behind. I used a wire wheel on them and it just spread them out and didn't remove them. My guess is it will take some paint thinner or something to clean up the remaining bits. Any suggestions?

[Bambikiller240]

Mineral Spirits (Paint Thinner) worked well for me and is much cheaper than Xylene, Lacquer Thinner, or Acetone. I'd wipe the entire surface with it to ensure a clean surface for whatever you have in mind for the metal. (welding, POR, Paint. etc)