Jump to content

SuperDave

How To: Use Dry Ice to Remove Tar Insulation

Recommended Posts

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.

P1030182_320x240.jpg

P1030185_320x240.jpg

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.

P1030192_320x240.jpg

P1030194_320x240.jpg

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.

P1030200_320x240.jpg

P1030201_320x240.jpg

P1030202_320x240.jpg

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.

P1030203_320x240.jpg

P1030206_320x240.jpg

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.


This post has been promoted to an article
  • Like 1

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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).

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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?

P1030258_320x240.jpg

P1030259_320x240.jpg

P1030260_320x240.jpg

P1030254_320x240.jpg

Share this post


Link to post
Share on other sites

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)

Share this post


Link to post
Share on other sites

I used Xylene to clean up the remaining residue. I also tried Acetone but Xylene works much better. It's the main ingredient in those goo remover products but is much cheaper and you can buy it buy the quart or gallon at places like Home Depot or Lowes, etc. It is toxic so wear proper breathing protection.

Share this post


Link to post
Share on other sites
I used Xylene to clean up the remaining residue. I also tried Acetone but Xylene works much better. It's the main ingredient in those goo remover products but is much cheaper and you can buy it buy the quart or gallon at places like Home Depot or Lowes, etc. It is toxic so wear proper breathing protection.

I got a xylene product and it worked very well. Only took moderate elbow grease and now all the remaining bits of tar are gone and the bare metal looks nice an clean. Well...at least the parts that aren't all rusted look nice and clean.

Share this post


Link to post
Share on other sites

I was thinking about using the dry ice technique, for I am having one hell of a time with the transmission tunnel. I did the floors, and they weren't too bad, the tunnel is worse for me.

Although I had some thoughts and concerns with the day ice maybe somebody can help clear this up. Is it possible to damage the metal by exposing it to such cold temperatures, maybe even crack it? We have all seen objects such as tennis balls surrounded in dry ice, and then they shatter like glass. I just need some re-assurance

Share this post


Link to post
Share on other sites

I'm not a chemist, but I believe the shattering tennis balls of which you are thinking were dipped in liquid nitrogen. Thanks for the write-up by the way. I've been having some difficulty getting all that tar mat off the interior.

Share this post


Link to post
Share on other sites

There is a big difference in the temperatures involved. I don't have my Chem book handy, but LIQUID Nitrogen is (if memory serves) MUCH colder than SOLID Carbon Dioxide.

That is because Carbon Dioxide (CO2) does not pass through a liquid state at normal pressures. You have to have an ungodly amount of pressure to keep C02 liquid. It sublimates from a solid to a gas while gaining thermal energy and taking it away from the metal it comes in contact with.

Yes it hardens the metal but you'd have to strike it just right at the exact spot that the metal has begun to crystalize (and that takes time) for it to crack it. I'm not saying it can NOT happen, just that it takes very special conditions for the famous shatter the metal with a hammer strike experiment.

Enrique

Share this post


Link to post
Share on other sites

Yes, a Large difference in temps.

A block of dry ice has a surface temperature of -109.3 degrees F (-78.5 degrees C)

Nitrogen changes from a gas to a liquid at a temperature of -320 ºF

Share this post


Link to post
Share on other sites

Superdave, thanks for the write up. I took your advice and gave it a whirl on my hatch bed. It worked excellent! After doing the entire transmission tunnel and floor boards by hand, the dry ice was a gift from heaven.

The clean up with the dry ice is minimal! If the dry ice technique is done when it is fairly chilly outside no water condenses on the ice. So therefore there is no clean up other than the pieces of tar paper that are removed, and they get as large as 6" x 12". Because the pieces of tar mat are removed so easily, there is barely any residue left behind, so the need for xylene and scrubbing will be minimal

Although I did have one problem. I did not purchase enough dry ice. When I got to the dry ice place, about 20 min. from my house, it turns out I only had $5 so I could only get 3 lbs. It just barely covered it, but the sections that had more dry ice on them came up significantly easier. Even 3 lbs. was enough to make the job only take about 20 min. of labor after the dry ice sets in. Sorry I could not post my pictures yet

All in all, a perfect thumbs up. I recommend it to all who need to remove tar paper

Share this post


Link to post
Share on other sites

this is a stupid question i realize, but why remove the tar mat? i am restoring my 280z, and i was going to just leave mine alone since there is no rust. it doesnt look pretty, but it reduces noise compared to no tar mat and it is covered by carpet anywho, so why remove it? is there any reason besides to remove rust? thanks for putting up with my stupidity :)

mark-

Share this post


Link to post
Share on other sites
this is a stupid question i realize, but why remove the tar mat? i am restoring my 280z, and i was going to just leave mine alone since there is no rust.

There is almost always rust under the tar mat. If you really don't have rust please post some pictures of your floor pans.

Share this post


Link to post
Share on other sites

Under the majorty of the tar mats there was no rust, except for the floor boards. Transmission tunnel, and hatch bed were good!

Many guys remove floormats if they are doing full restorations, they want to get rid of the old, gross, problemful mats. Eventually the mats will trap moisture and cause problems, so for a full resoration guys normally remove them so the entire car can be painted, then new sound deadening or thermal insulation can be installed

Share this post


Link to post
Share on other sites
...i was going to just leave mine alone since there is no rust. ...any reason besides to remove rust?.....

I don't think you can use the first sentence and a Z in the same breath, let alone claim it.

The main problem with the tar paper is that Datsun originally put it directly on top of unpainted sheet metal. Then they painted the car. Now maybe by the time the 280's came around they were painting first. Unfortunately the 280's I worked on only needed cosmetic body-work and I left the tar alone so I can't confirm nor deny whether it is there or not. You have to decide.

Just be aware that the initial body style Z (Series I and II) is notoriously prone to rust even in storage. The phrase Rust-Free Z is a dead give-away that you ain't checked her out yet.

As far as the second sentence, if you had cancer would you opt to NOT do anything because you didn't want a scar?

Enrique

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Who's Online   1 Member, 0 Anonymous, 198 Guests (See full list)

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.