Chavant and Di-NOC

An unsung car design essential under the microscope.

Get it while it’s… hard? Image:

We’ve simply never found anything better.

Prosaic words in a modern world where the non-use of a computer or software could be deemed a disability – thank heavens then for a material still requiring skilled human hands to shape and form – clay. Used for eons, clay in the automotive industry requires chemical alterations. Natural clay requires baking to gain its strength and rigidity but which renders the product non-alterable. To allow for modelling complex curves or knife-sharp edges, natural clay contains added oils or waxes and in the early days a volume filler, (sulphur) to maintain its pliable attributes.

Delivered in blocks (or billets), once warmed through, the clay can then be applied to a rudimentary shaped wooden buck or wire armature in clumps, literally thrown on then hand kneaded to express a basic shape. Once air dried, this automotive modelling clay maintains its malleable state and allows the skilled human along with a variety of hands tools to begin the sculpting process.

Apologies in advance – a potted history of clay use. Harley Earl is frequently considered the first exponent of such modelling clays in the late 1920s. Deeper research has found many other American carroseries were making scale clay models as early as 1912. Packard, Cadillac and the Mullins Body Co still leaned towards wood for a full scale model when showing prospective clients.

Earl, aged around sixteen was on a family summer holiday when he showed his younger brother, appropriately named Art, his skills with the natural form, according to an interview made in the ‘80s. Taking a fistful of orange clay, he deftly formed several small cars only for the elements to wash away his handiwork. Once Earl was installed in his father’s, then Don Lee’s workshop, this allowed his 3D skills to shine, creating life size cars from far more responsive imported European clays.

Allowing customers to not only see but alter their design took Earl to GM where, once comfortable in his environs, had the Research laboratory examine the ideal clay composition. Consisting of approximately ten percent natural clay, thirty percent wax and the remainder sulphur, this mixture was brought to life – but not by GM – a Red Bank, New Jersey based firm known as Chavant Inc. 

1958 GM Firebird 3 clay model. Image: The art of American Car Design

Now regularly suppled, once the models were sculpted, the painters took over, coating the clay with a milk based liquid named casein which once dried could be painted accordingly. There are stories of employees wanting to open doors and sit inside, so lifelike the models. Such is the industry’s way that progress let the casein drain away in the 1950s, supplanted by a foil-like film that would adhere to the clay surface with little more than a misting of water and deft hands. 

Manufactured by 3M (Minnesota Mining & Manufacturing Company), Di-NOC initially arrived in basic colours of black, silver or red, soon moving on to practically anything the eyes desired, including wood grain effects. The transformation was highly effective. Assisting in maintaining that realistic approach were Safalloy, a low melting point metal that could be easily shaped into items such as door handles, badges, mirror arms and bumpers, then buffed highly to represent chrome. 

1959 Buick clay proposal. Image: GM

Within the industry, speculation is open inasmuch who actually saw what(1) but Ford and GM had in the early clay years different specifications. Ford’s clay had a grey-green tinge and once dry was slightly harder. The General’s blend was of a redder hue and softer whilst rival, Chrysler obtained a clay who had a lower operating temperature, their supply being rival American Art Clay Co.

Industry standards eventually brought about the buff or tan coloured clay we see today whilst ditching the sulphur content. Modellers proved vocal over not only the clay’s aroma but also the dermatological effects. Sulphur’s eventual removal came about through the element corroding electrical contacts on (now) nearby computers and machinery. Actual clay property content is as closely a guarded secret as the cars the stuff helps generate.

Modern techniques still see craftspeople scraping and checking by eye, both hand and floor covered by curled sheaves of matter. The 1980s saw investments from computer guided milling and measuring machines arriving at appropriate times in the process. That old wooden buck has become a styrofoam block with the clay (on full size models) being an inch or two in depth. “Full sized clay models would weigh up to ten tons!” says recently retired FCA (as was) designer, Joe Dehner, speaker of the opening gambit.

He firmly believed in clay’s use; “Clay is quicker, people can get around the car, alter plans, brainstorm in 3D, see mistakes and if you cause one just add or remove more product. Technology helps the process but clay just works so well.” He should know, spending thirty years removing the stuff from his fingernails.

Support for clay remains strong; within the larger organisations workshops getting through a hundred tons per year, a similar time span a typical model takes in order to become a surface available for exact engineering dimensions prior to production. Smaller scale items are often wholly made in clay before being clad in Di-NOC, being highly prized in order to gain top brass approval. Scaling up in clay may reveal problems, perhaps over emphasising details or exacerbating radii, for example. A few flicks of the wrist can easily regain balance.

The use of real headlamps or door handles has condemned Safalloy to the history books, too before the all important Di-NOC coating reveals the new model in all its glory. Nowadays, this material can be found wrapping existing cars in shades not normally offered by the manufacturer and can last from between three and five years before requiring re-application. Another feature being advertising resigning the sign writer to custom work.

When hurled, mud sticks. Adding oil and finesse can create masterpieces. Clay should stick around a while longer. I’ll get my smock.

(1) Clandestine sorties attempting to see what the opposition were up to is nothing new. Back then a fedora, tie and stern face are today’s spyware.

Data sources: A Century of Automotive Style by Michael Lamm & Dave Holls/

Author: Andrew Miles

Beyond hope there lie dreams; after those, custard creams?

16 thoughts on “Chavant and Di-NOC”

  1. Every now and then one learns about the history of something that is so ‘normal’ in a certain field that one completely forgets about it. Maybe I should have used ‘I’ instead of ‘one’. Clay is one such thing and indeed an unsung essential. Thank you for enlightening me, Andrew. Fascinating stuff.

  2. Fascinating stuff, thank you Andrew. I hadn’t realised that the material used to wrap cars these days was actually Di-NOC.

  3. I know a professional clay modeller.
    Amongst the tools he uses are used hooks, spatula and drills from several dentists he regularly visits to collect the stuff that is no longer fit for their use but perfect for his.
    The amount of time going into detail work is astonishing. It takes about a week to create an outer door handle (that can be used as a pattern for the production die) and even longer for a rubber floor mat (you create a pattern for one single rubber square, then make hundred squares and fit them together).
    That guy also has a severe cold every couple of weeks when it’s his turn to go into the wind tunnel and make changes to the cars with the wind machines still running..

    1. I had no idea, Dave. Thanks for the added information. I’ll have an appointment with my dental hygienist next week. I’ll be thinking of clay models for sure.

    2. John – I was wondering if said cold would unfortunately prevent him from being able to go to work and spend the day in a gale…

      A few years back I had a tour of (parts of) the Ford Australia design facility, including their clay model milling machine – the grunt work can be done through the night by the machine and the modellers do final tweaking etc. It’s definitely down to a fine art now – but still doesn’t prevent outcomes like those from the show the other day!

  4. Fascinating Andrew so thank you for enlightening me on the use of clay. Another learning day! I honestly thought that 3D computer modelling had taken over and am received to find it hasn’t yet.

  5. Apologies are not remotely appropriate, Andrew – this is exactly what is so appealing about DTW and makes it compulsory daily reading. I am indebted – and enlightened. Thanks, too, to Dave (above) for extra detail.

    Interesting that the process goes back as far as it does – rather like the popular misconceptions regarding metallic paint, which also around since before the 1st World War

  6. Interesting insight Andrew, thank you. Loved playing with plasticine as a child and even then, tried making model cars, not very successfully I might add. Keep your great articles coming Andrew.

  7. Very interesting and original subject choice Andrew- thank you for this. Good to see that it is still being used to this day; one thing I remember reading a long time ago about the full size clay models is that when they were put outside for review by styling and corporate bigwigs and it was a hot and sunny day, they would sometimes start to droop and small parts such as badges succumbed to gravity or even fell off when left exposed to the sun too long.

  8. The clay model at full-size works in a way a screen-based representation does not. I believe it has something to do with the way a 3D image is projected on the spherical surface of the retina and with the way the object is perceived in real space. The 2D image is only an approximation of how a 3D object image lands on the eye. What might look good on a screen may not work in 3D as well. It´s subtle. However, a firm that eliminates clay modelling is gambling on a big investment, reducing the certainty of the design being as good as it can be. You may as well ask designers to use less paper – sure it saves money but undermines the entire point of the project.

  9. Afternoon all and thank you for your supportive comments. The link is to an eleven minute video about another American adopter of the clay model; Gordon Buehrig, which certainly adds weight to Richard’s pointers. These chaps had deep reserves of patience but look at the results. One wonders if any of these models survive.

  10. Thank you, Andrew. Very informative — even as someone who worked at one of the companies mentioned (though not in the division that supplies auto manufacturers).

    DI-NOC, by the way, is trademarked as all upper-case. It also has an extensive life in architectural circles, for many of the same reasons it is so popular in the automotive world.

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