Golden Gate Bridge Paint Myth

Myth about use of Golden Gate Bridge Paint on IBM 350 disks

An example of an urban legend from the RAMAC program

Why it's important
It is an urban legend that the coating used on IBM 350 disks was in some way similar to the paint or primer used on the Golden Gate Bridge. Until the 1960s the Golden Gate Bridge was actually primed with a non-magnetic red lead primer and painted with non-magnetic red lead paste in a linseed oil carrier. On the other hand, the IBM 350 disks were coated with a paint containing magnetic (gamma) iron oxide particles so that there is little or no relationship between the bridge paint or primer and IBM 350 disk coating other than perhaps the color. The source of the urban legend may have been the vendor of the original paint who mistakenly thought the paint he sold to be the same as Golden Gate Bridge paint.

A Google search of, "Golden Gate Bridge" RAMAC , will return more that 100 hits, most of them valid, showing the extent of this urban legend. Some examples of this legend:
  • In his 1977 book on the history of IBM, San Jose, David Kean described the disk coating as a "paint base similar to that used as a primer for the Golden Gate bridge." [1977Kean]
  • In 1989 Rey Johnson (IBM Laboratory Director, when RAMAC invented) stated, "The oxide paint we were using was essentially the same as was used to paint the Golden Gate Bridge." [1989Johnson]
  • In 2006 Bill Healy, senior vice president at Hitachi stated, "The disks' surfaces were covered with a paint that had magnetic properties--very similar to the paint used on the Golden Gate Bridge," [2006PC]

In July 2008 Bill Carlson an HDD WG member with extensive experience in disk recording media pointed out that this urban legend was "technically incorrect" since the Golden Gate Bridge paint "used a non-magnetic form of iron oxide." Apparently Bill, like many, thought the reddish color of the bridge was caused by iron oxide (rust) used as the pigment. A quick investigation determined that the bridge paint and primer pigments at the time of RAMAC development were lead oxide which in some forms is a red material.

Ordinary rust, that is, non-magnetic alpha-Fe2O3 iron oxide is red in color and frequently used as a colorant in paints. Its color is similar to that of the original red-lead paint and primer used on the Golden Gate bridge. Magnetic iron oxide has the same color and formula Fe2O3, but a different "gamma" crystalline (spinel) structure. Gamma-Fe2O3when compared to ordinary rust is a material that is manufactured by relatively expensive and at time patented [1954Camras] process.

Production formulations of IBM 350 disk coatings used gamma iron oxide in IBM invented binder systems, such as polyvinyl butyral combined with butylated melamine [1959Hagopian] and an oven-cured epoxy including phenolic resins [1962Johnson]. This latter formulation remained the basis of disk recording until adption of metallic thin film media. Other media vendors (3M, BASF, etc) used different binder formulations, but all used gamma iron oxide. The Golden Gate Bridge paint used oil as its binder which is not like any of these binders. We do not today know what binder was used with the Golden Gate Bridge primer; however the Johnson patent states no known binder system on the market met the impact durability requirements for the RAMAC disk coating and therefore a "research project" was set up leading to the disclosed invention. It seems unlikely such a binder was used in the Golden Gate Bridge primer. This summary table shows the lack of relationship between production RAMAC coatings and Golden Gate Bridge paints and primers:

IBM 350 coating
gamma iron oxidepatented Melamine or Epoxy systems
Bridge paint
lead oxidelinseed oil
Bridge primer
lead oxidecommercial epoxy

For the very first experimental disks the magnetic material was 3M red oxide mixed about 50-50 with varnish. This mixture was sprayed on the primed surface and baked for 45 min at 136 F. [1953Haanstra]

Bill Crooks was the engineer at IBM San Jose who part of the development of the first disks used in the IBM 350; it's his hand shown pouring "paint" from a Dixie cup on to a spinning RAMAC disk in several classic publications. His oral history was taken, in part, in order to investigate the source of this urban legend.

Crooks purchased the initial paint used for RAMAC development from a local paint store where it was known as "Red Barn Paint" but the store proprietor believed it was the same as "Golden Gate Bridge paint." Crooks so described it to his colleagues at IBM San Jose thereby possibly promulgating the myth. Bill purchased the store's entire supply and then procured additional supplies of magnetic paint from 3M, which was entirely consumed in the IBM 350 prototype disk development. According to Crooks, at least the first 10 IBM 350s were built [most likely 14 in total] with the magnetic 3M paint. There is no doubt that 3M had the capability of supplying paint with magnetic iron oxide particles. He recalls 500+ disks having to be air dried all over the San Jose Lab.
Subsequent to his oral history Crooks' recollection was disputed on the basis that it was unlikely that a commercial 1955 paint (i.e., the "Red Barn Paint") would contain the high loading of gamma iron oxide magnetic particles that came to be used in magnetic recording. There is no doubt that cost would have precluded a high percentage of gamma iron oxide magnetic particles in a 1955 commercial paint but it is also true that the bit cell size of the IBM 350 was so large by modern standards such that only a small percentage of magnetic particles would produce a magnetic paint. Such particles might be present in a commercial 1995 paint as an impurity or as an additive to achieve a property such as color.In 2007 a RAMAC disk was characterized ausing modern techniques;[2007Jung] the particles were neither the expected acicular shape of gamma iron oxide nor its expected coercivity of about 350 Oe. Such a disk is consistent with Crook's recollection.
There is no question that in 1955 3M could produce magnetic iron oxide particles at will, they manufactured magnetic tape for IBM. 3M was contacted regarding the compostion of its 1955 "Red Barn Paint" but was unable to provide any records.

Additional Information
Oral History of William (Bill) Crooks, Computer History Museum, Mt View CA, Accession Number 102702016, p 10-11
[1953Haanstra] John Haanstra's lab notebook. June 3, 1953
[1959Hagopian] US Patent #2,914,480, MAGNETIC COATING COMPOSITION. Jacob J. Hagopian, Nov. 24, 1959
[1977Kean] Kean, David W., "IBM San Jose, A Quarter Century Of Innovation”, 1977, CHM accession number: 102687875
[1989Johnson] Dinner Talk by Rey Johnson at the DataStorage '89 Conference, San Jose CA, September 19, 1989
[1954Camras] US patent # 2,694,656 by Marvin Camras describes a complex commercial process for making the magnetic form of iron oxide
[2006PC] "The Hard Drive Turns 50... ", Melissa J. Perenson, PC World, Sep 13, 2006
[2007Jung] Study performed by Hong-Sik Jung at Komag, now Western Digital, Automation Parkway, San Jose CA

Provenance note: This article was written by Tom Gardner with contribution by Bill Carlson. Revision 29 of this article was reviewed and approved by the Computer History Museum's Storage SIG on June 20, 2012.

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