1969 Z/28 firewall crayon marks, question?

[Bryan302]

I was reading some old post on firewall crayon marks from William and Keech.  When stripping a firewall and expecting to find grease penscil marks on the bare metal, what is the best effective method to strip the paint?  Some say soda, some say rubbing with laquer thinner or reducer.  What works the best without harming the expected find?

Thanks,
Bryan

[BULLITT65]

Great question, for those you who have "discovered" your crayon marks. Please post pictures of what you have been able to recover.

[william]

We used soda blasting on the '67 Z/28 project of many years ago, sorry pics pre-date digital.

Don't sand-blast. After 38 years in the hobby I avoid it as much as possible.

[BULLITT65]

I know what sand blasting is, and I know what media (plastic) blasting is. What is soda blasting?

[william]

Soda, media, essentially the same thing.

[69pace]

The media used to blast is sodium bicarbonate a.k.a. Baking Soda

[BULLITT65]

thanks for the info. so is there a method of revealing the crayon marks and still preserve the existing surfaces?

[BillOhio]

I used soda and found a lot of writing. Had mar for maroon, n10, ok. It looks like the pencil stains the bare metal. I don't know how anything would take off paint and leave pencil material. Paint should be tougher. I will try and post a couple

[BillOhio]

If you use soda, it leaves a residue that inhibits rust but paint doesn't like it. I soaked mine with acetone and had no adhesion problems

[BillOhio]

Soda won't do much on rust either. N10

[BillOhio]

Ok

[BillOhio]

404 at top bottom might be mos?

[BULLITT65]

Bill,
your the man, great pics. So I know you see the Camaros at shows with all the paint dabs and crayon marks all over everything after it has the finish paint, (ex: engine compartment) . I have the "PTB" stamps on my firewall, but would any 69 camaro have left the factory with crayon marks on the black paint on the firewall, or were the crayon marks only and always used before paint?

and a follow up question: why do you see front license plate brackets with out the license plate but then a white "X" in crayon?

[BillOhio]

I thought I saw a car on here once where you could see the color name. Under the mar on mine is 21. You can see it. Don't remember if there was an m. I think there was.
I think it would be unlikely anything should be visible unless the grease was so heavy the paint fell off. The mar on my car does look different than the other marks.
I don't know on the plate bracket. Did I show you where gm is wrote on my fender extensions? It and firewall writing is very fancy!

[william]

There are survivors with visible crayon markings and the explanation is simple. Paint did not always adhere well to the grease pencil and quickly flaked off. The markings were done by Fisher Body during body fab to guide the workers. This was long before any paint; firewall blackout was done after the car was painted. Remember that the next time you see a restored Camaro with the paint code written over the blackout.  

There was a marking made after paint that is often visible. The unit number has been seen on sub frames, and inside the lower grille panel.