The Official 356Talk Forum

The discussion above regarding undercoating has overlooked the most important step in the process! And that is to clean the bare metal with metal prep and then apply a self etching primer. This will minimize or eliminate future rusting. Also, the importance of using seam sealer on all joints, such as floor pan overplapped areas, rocker panels and step plate joint, front and rear closing panel to inner panels, should not be over looked.

Tom Scott

Agreed Tom, that should be a given. I have media blasted all areas and then hosed everything down with Epoxy Primer. It almost looks powder coated. I doubt it will ever rust again. It is very difficult to imagine spraying such a pretty surface with tar. As I posted elsewhere, I am finding it difficult to simply spray tar over all my hard work. I see why these cars are over restored. Once all the work is done, who wants to make it look so messy like the factory did.

I know what you mean - here's my cab before and after applying the undercoating

Reviving an old thread here.

Anyone know what was originally used by the factory for undercoat? The evidence so far:

1) Here's a translation of a caption for a photo in Jung's Reutter book showing a worker applying undercoat with a spray gun to the bottom of a cabriolet shell on a rotisserie in 1953:

• Before painting, the body shell is sprayed with sealing and sound-absorbing compounds in a special rotating device. Approximately 20 kg deadening and underbody protection (Terosol) are used for protection and to reduce noise. The previous design was unfavorable because the paint had to be applied overhead. This new, labor-saving and material-saving device comes from Karl Cless (equipment construction). It was immediately nicknamed "Ox Grill."

2) In the classic Made By Hand film, you can see the Reutter schutz man using Terosol on the Ox Grill (starts at 9m45s). 3) Some folks over at the Early 911S forums say Teroson was used on the SWB 911 bodies. Perhaps this is the same stuff, or some variation on it from the same company? Today you can buy Teroson and Terotex schutz products.

http://www.loctite.com.au/aue/content_d ... ochure.pdf

Has anyone used Teroson for their restoration? I suspect modern products are very different from the old, even if the same brand is used.

Anyway, I would be interested to learn more.

One 4th bit of evidence. From the 1956/57 Reutter "Maintenance Instructions for Porsche Bodies" booklet, the last page has a cleaning compounds order form. One of the items is

Teroson, droplet and rain seal cement

I assume this is touch up sealer for the underside.

Also interesting to see the period polishes recommended by Porsche too, including Simichrome.

Porsche 356 factory under seal, Teroson sealing cement formula:
3 parts roofing cement / 1 part fine mica
https://www.homedepot.com/p/Henry-0-90- ... /100080447
https://www.ebay.com/itm/302344246767
Mix, dab on with a brush. Give it a week or so to dry.

Indistinguishable from factory original undercoating

James - Simichrome is still available! The maker is Happich. I've used it since the 60's - great stuff - really makes aluminum and brass shine. Actually, it looks like I still have the tube from the 60's - maybe it's time to clean that drawer out ....

"3) Some folks over at the Early 911S forums say Teroson was used on the SWB 911 bodies. Perhaps this is the same stuff, or some variation on it from the same company? Today you can buy Teroson and Terotex schutz products."

Actually, I was just grubbing around the bottom of my 912 project today and took this picture. Car built at Porsche factory in Sept. '65
Looks like the same stuff I scraped off of my C cab built in May '64.

It is my belief that the factory used Teroson on the 901 series body’s, but without the mica mixed in with it. At least there was never any mica on any of my early 911’s. My current 59 coupe has Teroson both with and without mica mixed with it, in different areas. The guys in the factory mixed and matched, sometimes randomly you could say. I have always spent way more time under my cars than I ever did driving them.