Asphaltum

Asphaltum has a variety of applications: as a pigment for oil painters, as a resist for glue chipping glass panels and to tone gilding. 

By Jim Hingst @hingst_jim

Asphaltum is a dark brown, oily liquid that smells like tar. While the two might smell the same, they are definitely different materials. Tar is a by-product of the distillation of coal. Asphaltum, on the other hand, is a by-product of oil refining.

Many of the old sign painters used asphaltum for paintings and to tone gold leaf work. Prior to Prohibition, they also used it as a resist when making glue chipped glass signs.  In the area of fine art, the old masters also used this pigment during the middle ages and the Renaisassance.

One way that fine art oil painters used asphaltum was to dissolve it in turpentine before mixing it into an oil medium. Others first burned the asphaltum and then crushed the residue before adding it to linseed oil.

For my reverse painting on the second surface of a glass panel, I used a mixture of asphaltum and quick rubbing varnish for shading.

Although asphaltum has a long history, its use by artists of all types has fallen out of favor for a variety of reasons. Some questioned the lightfastness of this colorant. Others complain that the use of asphaltum can contaminate surrounding colors in a painting.

I have not experienced any of these problems. I have used asphaltum for gilding on the second surface of glass before laying on gold or metal leaf. Because it is transparent, the warm brownish colorant is wonderful for shading. Used for this application, the asphaltum should be mixed with quick rubbing varnish to ensure good adhesion to the glass.

For second surface gilding on glass, I gradually built up the density of the shading in the foliage and the scroll shown above.

To tone first surface gilding, a mixture of Japan earth-tone paints, asphaltum, quick rubbing varnish and turpentine was used to give the gilded Antebellum Era carving (shown below) an aged appearance. After applying the toning mixture to the surface, the excess was wiped off of the high points, leaving a heavier deposit of the glaze in the recessed areas of the carving.

For the purposes of glue chipping, asphaltum, which is an oily substance, is used to repel the water-based animal hide glue. Remember, oil and water don’t mix. Functionally, the asphaltum forms a mask that gives a clean crisp edge to the glue chipping. See the photo below. Without it, the glue chipped edge may be ragged.

If you are interested in using asphaltum for any of the applications that I have described, you can buy it at Letterhead Sign Supply (www.letterheadsignsupply.com). A half pint will cost about $10.00.

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About Jim Hingst: After fourteen years as Business Development Manager at RTape, Jim Hingst retired. He was involved in many facets of the company’s business, including marketing, sales, product development and technical service.

Hingst began his career 42 years ago in the graphic arts field creating and producing advertising and promotional materials for a large test equipment manufacturer.  Working for offset printers, large format screen printers, vinyl film manufacturers, and application tape companies, his experience included estimating, production planning, purchasing and production art, as well as sales and marketing. In his capacity as a salesman, Hingst was recognized with numerous sales achievement awards.

Drawing on his experience in production and as graphics installation subcontractor, Hingst provided the industry with practical advice, publishing more than 150 articles for  publications, such as  Signs Canada, SignCraft,  Signs of the Times, Screen Printing, Sign and Digital Graphics and  Sign Builder Illustrated. He also posted more than 325 stories on his blog (hingstssignpost.blogspot.com). In 2007 Hingst’s book, Vinyl Sign Techniques, was published.

© 2015 Jim Hingst