Leslie R. Henry's book "Model T Ford Restoration Handbook" states in one chapter that the Ford body line moved at 25 feet per minute. When the bodies were taken off the line to be primed and placed back on, they then went to the infamous paint section where two men painted both sides of the car at the same time with what resembled "water sprinklers".
After painting, the bodies moved 200 feet where they were dry enough to be removed and stacked for drying (a 24 hour period). If they were dry enough to handle within 200 feet after having been sprayed, that means that the paint was "touch dry" in 8 Minutes!!!
How accurate is that?
That sounds about right, especially if they were using lacquer. I painted my '24 Touring with lacquer and by the time I had gotten all the way to the other side of the body, the spot where I had first started would already be dry to the touch.
They were using "Japan" enamel.
I doubt if the Japan enamel was touch dry at that time, that doesn't mean they could not then handle the bodies. Once the paint had tacked off ( no longer could dust stick to it) it could then be moved. The bodies would have been manhandled without touching anywhere that mattered.
The fact they cured for 24 hours means the paint was slow to dry completely. Lacquer was not used at that time and it has to be sprayed it would not be able to be hosed on as was the enamel.
The reference in Les Henry's book doesn't mention the year. Ford improved the painting from the early T's that were blue/black and may have needed more drying time,... to the later Japan enamel that was air dried in huge forced air blowers on the assembly line. Later the Improved cars got the pyroxylin paint that dried super fast too.
1915, in the famous Ford color
early '26 with Japan enamel
Pyroxylin later in '26, note the air handling to dry the body.
I always thought that japan enamel was just a fancy word for lacquer.
Besides, in true japanning, the bodies would have to been heated to around 400 degrees (F) to bake the paint on.
Read "Ford Methods and the Ford Shops" starting on page 360, "How the Ford Bodies are Finished. Painting, Upholstering, Japanning and Baking."
The first brown metal primer coat was done in a spray booth with an atomizer.
The following were flowed on with the body traveling on a track and the bodies were set aside for drying between coats and rubbed prior to the application of the subsequent coat:
blue black primer coat
first color varnish coat
second color varnish coat
finishing varnish coat
Page 362 says "After the body has traveled about 200 feet, it is sufficiently dry to be removed and stacked for drying, which takes 24 hours."
You can interpret the above any way you want. It does not necessarily mean that the paint was "touch dry." It may mean that it was dry enough so it wouldn't run. Also, when they removed the body from the track they probably had specific methods, tools and fixtures for handling a wet body such as racks, trucks, or dollies, etc. so they could move the bodies without physically touching a wet surface.
Also, the chapter mentions that it took 200 feet of travel (at 25 feet per minute mentioned earlier) for the excess paint to drip off the car in the tank below. This supports a hypothesis that the bodies were no longer dripping paint when they were removed from the track, not necessarily "touch dry."
The terms "lacquer", "varnish" and "enamel" can be confusing as they had different meanings over the years. DuPont's DUCO was the first of the fast-drying nitrocellulose lacquer finishes, but the term "lacquer" could also mean shellac, tree resin or other finishes before that. Another not-so-new finish is "clear coat". Many brass-era cars and carriages had a clear top coat, also.
Wow! without a mask, sniffing those fumes day in and day out, I wonder how long those painters lasted before they started losing control of their faculties as their brains were gradually and irreversibly damaged. Were they even aware of the dangers of prolonged exposure to paint fumes? Jim Patrick
Paint can be considered "dust free" or "tack free" within a few minutes. This just means that the surface has dried enough that dust won't adhere to it. This does not mean it can be handled and is by no means dry. Tack time varies by the type of paint. The movement of painted parts was done by equipment not a bunch a guys grabbing and lifting.
They used primer? What was the primer?
If the paint dried that fast how did they keep it flowing in the drain troughs? It also seems that you would have to add some sort of solvent to the paint that's being recycled through the system.
RE: Jim Patrick and mask comment -
Part of the caption that goes with the priming booth photo:
"This is a posed picture, the paint spray making photography impossible under ordinary working conditions. The workman wears a mask whenever he is actually painting."
Okay, here's the thing I don't understand:
I'm told that at the peak of production, Model Ts were being assembled in ninety-three minutes. But how can that be if it took several hours for the paint on a body to dry? Heck, even I know that an assembly line can only move as fast as its worst bottle-neck.
Bob, the speed at the painting line was at least as fast as the assembly line - but they were a day ahead with their production
There is no confusion as to what a lacquer , enamel or varnish is they are all different.
A lacquer dries by evaporation. it can be redissolved by putting its solvent onto it. They require lots of solvent to allow application usually they dry so fast you have to spray them as most of the solvent evaporates on the way to the surface, You get thin coats and have to put on multi coats. if you hold the gun too far away it will arrive too thick or as dry spray.
An enamel dries with a minimum of evaporation and then a reaction takes place with oxygen in the air ( that's why you get a skin on the top of the paint even when its in a tin with the lid on.) Being thinned so little you get a thick coat so runs can easily occur. Fumes would have been less of a problem with them all that was needed was reasonable ventilation.
Varnishes usually refer to finishes derived from natural products such as boiling down vegetables matter, tree saps and the like. Used for hundreds of years they don't work as well as those found by chemists.
The faster the paint dries the less gloss you get so lacquers usually require buffing to final gloss , enamels and varnishes dry glossy. All these paints are clear or have a yellow tinge to them, color is added by using pigment.
We lost the use of clear over the color with Duco as its clear is horrible and goes off in the sun quickly. Once new clears were found they again came back.
The flow system required the paint to be reduced to a thin enough consistency to work. As the paint dried so slow little solvent is lost out of the excess paint pumped back to the tank to again pour onto the cars. The viscosity ( how thin or thick the paint is) was adjusted by adding some more solvent and or heating the paint. One of the standards used today for thinning paint is to use a Ford Viscosity cup used to measure the viscosity on the assembly line.
Don't know if anyone has answered since I started as I was called away
Bob, there was a very large store room to put the bodies in until the Duco eliminated the need to dry for so long. Once wood was largely eliminated they could then bake the bodies to shorten the time even more.
Kep, the primer was an enamel based one,
Although Ford called their process Japan Black...it wasn't a traditional "Japaning" process. Sort of loosely based comparison/association. Terms used in 'finishing' prior to the mid-20's for the most part are different that what the terms were used for after that time. The 'paint' industry when emerging was sort of like the emerging computer industry of the 90's....buzz words were great and became marketing definitions until everyone got totally confused and then hard definitions had to be made.
What is known is that when going from a 'varnish' based paint to these so-called 'japan finish' is that the logistics chain had an improvement on the order of 10::1.
As to your question...here are examples of some 'iron era' paints used by Ford...
Ford F-101, referred to as first coat black...
32% asphalt. Specified by Ford to be of a trade name Gilsonite for both consistency and adherence as Gilsonite never dries 100% hard where other generic asphalt dries harder.
3% carbon black pigment
10% linseed oil unboiled (Secret recipe yet unbroken, with lead and iron as the drying catalyst) Now turned into boiled linseed oil 'mix'
55% solvents of mineral spirits, or “turps”, or naphtha...apparently whatever was the cheapest commodity of the month.
Ford F-102, always referred to as finish coat black.
35% asphalt. Same Gilsonite requirement
NO additional pigment
10% linseed oil unboiled (Secret recipe yet unbroken, with lead and iron as the drying catalyst)
55% solvents of mineral spirits, or “turps”, or naphtha.
So we can surmise that the 'spirit's' went off quickly just as they do today and we were left with a 'film' that was essentially a 'tar' suspended in linseed oil at about a ratio of 3.+::1. Lead can do funny things...think catalyst, but I'm not aware of just how fast lead can work.
Think of it this way...how fast does the best boiled linseed oil dry today? It skins up relatively quick and same day seems dry but you can smell it for a month! That means it is still 'cooking'.
Oh, another point to mention concerning the question of recycle flow and the 'flash off' of the solvents and how to maintain a proper mix.
History lesson...Very advanced and scientific method...every now and then throughout the day, someone would dip a small ladle in the 'bath'. The ladle had a small hole in the bottom, perhaps 1/8" diameter. They would time how long the ladle took to empty the ladle out the hole. The 'time' told them their percentage of mix. A 50% solvent would take longer than a 55% solvent.
The time difference told them just how much 'virgin' solvent to add to the 'bath' Who needs computer control...lol
I thought I would share this with the forum . Ford only varnished the main body and hood apparently. the rest was Enamel Dipped. I also read that the final wipedown between coats was done with Gasoline.
This is from a 1923 Salesmen's Fordex guide.