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Richard, I do hope you never experience a delamination failure in your paintings, 30 years past, or 30 years into the future. Good on ya!
Here's the deal. There is no escaping the physical nature of certain materials. When dry, the surface of alkyd resin paint films is impervious to the chemical action and solvent transfer which allows traditional vehicles to bond. If an alkyd film is not abraded to provide a mechanical key for subsequent applications, it is not a question of whether delamination will occur, but how and when.
Having used alkyd paints for over 40 years in the production of commercial displays, I can tell you that this is not only a feature which is addressed by the manufacturers of commercial coatings, but is most definitely a factor in over-layering applications of alkyd paint.
To reiterate the history of alkyds, originally "al-cid", alkyd resin is a synthetic resin produced from the combination of alcohol and an acid. It was developed in the early 1930s out of the necessity of producing paint coatings which would be more durable in automotive applications than the traditional natural vehicle paints then in use. It was especially effective as a coating for automotive chassis.
This durability extended to the formulation of a wide range of "oil base" utility coatings, and its superiority for weathering and wearability has certainly been proven through the last 70+ years. It remains to be seen whether it will perform better through centuries than the materials and methods developed for oil paining over 500 years ago, but it's likely.
Avoiding delamination depends upon two factors. One is the obvious difference in application. Fine art paintings are never (one hopes!) subjected to the weathering and wear which utility coatings are, so not sanding between coats will cause a ready, obvious failure on, say a farm tractor, which is subjected to an environment an easel painting never will be.
Second, all is well so long as the work is produced entirely wet-in-wet, or overpainted during the brief "touch-dry" interval in which the "skin" of wet paint can yet be permeated by the vehicle in the overpainting, thus resulting in the homogenous melding of layers, rather than two "strata" separated by the formation of a cured alkyd resin layer.
Realizing contributions to fora such as this ever amount to nothing more than choosing to believe who is lying to you at the moment, I can only say that my observations are the result of 40 years of painting with a wide variety of materials, the examination of a fairly broad report of use by other professionals, and my own inquiry (however unscientifically proven) into the physical and chemical makeup of the materials which have come my way. I think artists of worth should know fully the properties of the paints they use, and should not be deceived by the claims of manufacturers and suppliers, who more often than not (particularly the past 30+ years) are far more concerned with their "bottom line" than in providing artists with proven, quality materials.
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