Con­ser­va­tor Mark MacKen­zie

Pasatiempo - - CONTENTS - CON­SER­VA­TOR MARK MACKEN­ZIE Mark MacKen­zie with his mul­ti­spec­tral imag­ing ap­pa­ra­tus, photo Olivia Har­low/The New Mex­i­can

THE Ste­wart L. Udall Cen­ter for Mu­seum Re­sources is only 14 years old, but it can be maze­like. In the midst of one of its war­rens is the for­mer stor­age room that Mark MacKen­zie calls his Fortress of Soli­tude. This is where he has his mul­ti­spec­tral imag­ing lab­o­ra­tory.

MacKen­zie, who has been the Mu­seum of New Mex­ico’s chief con­ser­va­tor for the past 12 years, de­signed (with some help) and built the equip­ment he uses to carry out pi­o­neer­ing in­ves­ti­ga­tions of two renowned Segesser Hide paint­ings. “This was a six­month project that turned into two years,” he said. “Th­ese hides are re­ally quite im­por­tant. They’re the ear­li­est ex­tant rep­re­sen­ta­tions of mil­i­tary ex­pe­di­tions within the geo­graphic United States, from the early 1700s.”

The Segesser I paint­ing de­picts a con­flict be­tween ri­val tribes­men, pos­si­bly in the El Paso area. In Segesser II, we view a suc­cess­ful am­bush by Pawnee and Oto In­di­ans of Span­ish troops who were dis­patched from Santa Fe to Ne­braska. The paint­ings’ sub­strate was be­lieved to be bi­son hide. “I was able to con­firm that,” MacKen­zie said. “I worked with a bioar­chae­ol­ogy team at the Uni­ver­sity of York in the UK, us­ing a new tech­nique they de­vel­oped for ex­am­in­ing parch­ment.”

As chief of the Mu­seum Re­sources Divi­sion’s con­ser­va­tion unit, MacKen­zie has many re­spon­si­bil­i­ties. He re­cently used X-ray flu­o­res­cence and a Geiger counter to as­sess po­ten­tial repa­tri­a­tion ma­te­ri­als for the Pue­blo of Acoma, and his unit is at work on a re­model of the Mu­seum of In­dian Arts and Cul­ture’s Here, Now & Al­ways ex­hi­bi­tion. But his Segesser project is un­de­ni­ably sig­nif­i­cant and in­trigu­ing. His col­lab­o­ra­tors have in­cluded Eric Hansen, for­mer chief con­ser­va­tor at the Li­brary of Congress, and Hansen’s suc­ces­sor, Fenella France.

Among other tal­ents, MacKen­zie is an in­ven­tor. He worked with a cam­era-sys­tem de­signer and a com­pany that makes au­to­mated plasma weld­ing tables to con­struct a com­puter-con­trolled trav­el­ing imag­ing gantry. It’s a mas­sive metal frame­work that in­cor­po­rates a large plat­form with a vac­uum ta­ble used to se­cure a paint­ing, and above that, a mo­tor­ized bridge. On the bridge is a high-res­o­lu­tion dig­i­tal cam­era made by Phase One. Us­ing a com­puter, MacKen­zie di­rects the bridge to move in pre­cise in­cre­ments over the plat­form; the cam­era moves from side to side.

The “mul­ti­spec­tral” part of the imag­ing equa­tion re­lies on a set of lights on the bridge. “We use very, very spe­cial light to take pic­tures in a dark room, start­ing with ul­tra­vi­o­let, then five slices of the vis­i­ble spec­trum, then five slices of the in­frared spec­trum. We wind up with a stack of 19 im­ages that re­veal dif­fer­ent as­pects of the paint­ings. It’s ab­so­lutely amaz­ing. I can ac­tu­ally see brush­strokes with this equip­ment. I was able to see through the paint, see down to the un­der­draw­ings.” Those draw­ings, used as guid­ance by the artist (or artists), have never been seen be­fore, he said.

The hide mu­rals are 54 inches by 18 feet. MacKen­zie di­vided them up into pho­tographed “tiles” of 9½ by 11 inches, re­sult­ing in hun­dreds of rec­tan­gu­lar im­ages of sec­tions of the Segessers — to­tal­ing about two ter­abytes of in­valu­able dig­i­tal in­for­ma­tion. “What I tried to do was not only an­swer ques­tions but cre­ate a data set that can be mined by re­searchers into the fu­ture.”

The en­thu­si­as­tic in­ven­tor brought out a pro­to­type hand­held me­ter that mea­sures and dis­plays am­bi­ent tem­per­a­ture, hu­mid­ity, and ul­tra­vi­o­let light — read­able in lu­mens and lux. “It cal­cu­lates all the in­for­ma­tion that con­ser­va­tors love when they’re try­ing to de­ter­mine whether dis­play­ing an ar­ti­fact will dam­age it,” MacKen­zie said. He is also an ex­pe­ri­enced wet-plate pho­tog­ra­pher who is look­ing for­ward to hold­ing work­shops us­ing his col­lec­tion of 8x10 view cam­eras. His ca­reer in­cludes stints as a con­ser­va­tion chief for Parks Canada, Winnipeg, from 1981 to 1991; then as a head con­ser­va­tor of the Western De­vel­op­ment Mu­seum in Saskatchewan Province from 1994 to 2006. “Ev­ery 10 or 12 years, I move. Jan­uary will be 12 for me, and I’m leav­ing this com­ing year,” he an­nounced. He and his wife, Janet MacKen­zie, who is the chief ar­chae­ol­o­gist with the Mesa Pri­eta Pet­ro­glyph Project, are plan­ning to re­tire to Canada.

In con­clud­ing his dis­cus­sion about the Segesser work, he em­pha­sized that his de­tailed in­ves­ti­ga­tion was be­gun at the in­sis­tence of Josef Díaz, for­mer cu­ra­tor of Span­ish colo­nial art at the New Mex­ico His­tory Mu­seum. MacKen­zie added that his mul­ti­spec­tral imag­ing equip­ment was funded in large part by a be­quest (shared with the Of­fice of Ar­chae­o­log­i­cal Stud­ies) from Don Pierce, who was a pathol­o­gist with a life­long in­ter­est in Na­tive Amer­i­can art, cul­ture, and the land­scapes of the West. A crit­i­cal goal of the Segesser project is the abil­ity to de­tect changes in the works and bet­ter pre­serve them. “Th­ese paint­ings are on skin, and col­la­gen ages to a stiff, crinkly tex­ture. We’re try­ing to as­sess where th­ese paint­ings are on the curve of ag­ing,” MacKen­zie said.

Equally im­por­tant is de­vel­op­ing new in­for­ma­tion about their cre­ation. “We didn’t re­ally know much about the pig­ments and me­dia, how th­ese paint­ings were ac­tu­ally con­structed. The blue paint should have faded by now, af­ter nearly 300 years. Many peo­ple thought it was Prus­sian blue, which is con­sid­ered to be the first syn­thetic color de­vel­oped, in about 1705. But I proved them wrong. This is an in­digob­ased blue, but it should have faded. I’m on the way to prov­ing that this is Maya blue. The Maya had fig­ured out how to marry indigo with at­ta­pulgite clay to make a syn­thetic blue, much ear­lier than 1705.”

MacKen­zie’s study of the newly re­vealed brush­strokes has con­vinced him that there’s “a good like­li­hood” that there were Na­tive Amer­i­can artists in­volved in the fi­nal­iza­tion of the art­works. A visit by rep­re­sen­ta­tives of the Pawnee Na­tion strength­ened that be­lief. “This is the old­est pic­to­rial rep­re­sen­ta­tion of their peo­ple, and they were amazed at the ac­cu­racy of the painted fig­ures and their re­galia from what they have been told. I be­lieve some­one who was present at that bat­tle was in­ti­mately in­volved with the de­sign of the Segesser II paint­ing.” — Paul Wei­de­man

“Th­ese paint­ings are on skin, and col­la­gen ages to a stiff, crinkly tex­ture. We’re try­ing to as­sess where th­ese paint­ings are on the curve of ag­ing.”

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