Question: Best Product to Replicate Factory Undercoating

I am looking for some advice here. I am nearing the stage of red oxide primer and undercoating on my 68 Cougar. I replaced a few panels, and some of the original undercoating has been removed. Can anyone recommend an undercoating that will replicate the factory color and texture?

Thanks in advance.

Which panels and where?

The car was put on a rotisserie and blasted with care so that the majority of the original undercoating on the rear wheel wells, rear axle forward and under the floor pans has remained on the vehicle. There are a few places that were loose and came off, as well as some areas on the outside of the inner fender areas and on the body just rear of the front tires. I would like to replace the undercoating in the areas it was removed from. Not sure if my description makes any sense.

Thanks for your reply,

Here is what I used on my Shelby. Remember, the floorboards are not done. 3M Schutz and you’ll need the applicator gun. Both items can be purchased on Amazon Prime.


In some areas you’ve mentioned (like rear wheel wells and trunk) the sound deadener will get painted over with body paint if you’re doing a restoration while in other areas the final look/color is more important since it will be the top coat. May of the products available are difficult to build up to the thickness they were originally applied to and if you try and build it to 1/4" thick each additional coat will dissolve the earlier coats which makes attempts to get the product to sag or produce “curtains” extremely difficult.

I’ve found success with using Spectrum Sludge an acoustical product Just checked the site and it appears they have changed the product and or renamed it as Second Skin. Looks very similar to the old product but haven’t needed to buy any recently

You can spray or brush it on then once you have the general look you want over coat it with a spray product that will add the fine texture and reproduce the sprayed on look around the edges helping it to bend and make it look like it was all sprayed on if you pay attention to shadows and such (example on the floor the emergency brake cables or frame edges) that would have been produced during the small number of passes with the original application wand.

Others have been happy with products made by Wurt or Lord Fusor but it take a special application and the tubes are fairly expensive

Hope this helps

Also I suggest that what ever product you choose to do some practicing and testing before hand. Hang some cardboard vertically and build corners with a couple of sheets to see how it applies, lays and builds. You may find that if you cool the product before you apply it it will coat differently - thicker

Good luck with your project

67427GT500 and J_Speegle, Thank you very much for the information, suggestions, and links. Last question, do either of these products cure to the brownish tent as the original?


Mixture of the product was asbestos (not a brownish material) and other chemicals. Some of the brownish tint on the surface (on those areas where it isn’t coated over) can be a collection of dust and dirt over time plus what ever dust and dirt (like on the firewall sealant) can be from what the still tacky surface collected in the plant and out in the holding lot after the cars were finish. Don’t know of any product that comes in brownish top coat except for some of the rattle can stuff. If you need that look you could build up with the products mentioned then top coat with the brownish product to finish it off

Going to take some testing to see if the look is right for you

Thanks, I will do some experimentation. I really appreciate your help, and have been reading through many of the posts on the Concurs Mustang Forum which seems to be a great source of information.


I found a canned product that does cure with a bit of a black tone. I’ll see if I have the can later this evening and post the product. I used it for a bit of quick touch up. I sprayed it out on a test surface first.

Sounds good Jeff.