Applications of Xâ€“ray computed tomography in particulate systems

A W E L D E R ’S S P A R K T O U C H E D o ff the attic fire in the Sevier C o u n ty Recorders O ff ice in R ich fie ld , U tah on M ay 2, 2006 , igniting a blaze that ripped through the craw l space consum ing the bu ild ings paper-backed insu­ lation. T h e fuel readily spent, the fire burned itse lf out 15 m inutes later, sparing the struc­ ture but coating everything below the rafters w ith fine, powdery soot. T h is carbonaceous residue filtered down through the ceiling tiles settling on everything in the offices below inc lud ing the historic courthouse record books stored horizontally on metal ro lling shelves w ith in the vault. About 300 nineteenth and twentieth century full-leather spring-back stationers’ bindings, many covered in protective white canvas jackets, were untouched by the fire but impregnated w ith a layer o f soot and reeked o f smoke. Front of the Sevier County Recorders Office (Richfield, Utah, USA) on May 9,2006, one week after the fire. Photo credit Randy Silverman

F rozen C02, which comes from liquid C02, used in soot removal is different than C02, which is produced as a by-product of another process.It is not excess C02 but C02 that has been reclaimed or recycled from C02 already existing in the environment Dry ice blasting, an environmentally conscious way to use existing C02 to our advantage, is environmentally friendly and not environmentally damaging.
Dry ice blasting pellets is environmentally friendly and contains no secondary contaminants such as solvents or grit media.They are non-toxic, nonhazardous creating advantages to the environment your employees, and production facility: D E R 'S S P A R K T O U C H E D o f f the a ttic fire in the S e v ie r C o u n t y R e co rd e rs O f f ic e in R ic h fie ld , U ta h o n M a y 2, 2 0 0 6 , ig n itin g a blaze that rip p e d th ro u g h the cra w l space co n su m in g the b u ild in g s p aper-backed in su la tio n .T h e fuel re ad ily spent, the fire b u rn ed itse lf o ut 15 m in u tes later, sp aring the stru c ture b u t coatin g everything b elo w the rafters w ith fine, p o w d ery soot.T h is carbonaceous residue filtered dow n through the ceiling tiles settling on everything in the offices b elo w in c lu d in g the h isto ric courthouse record books stored h o rizo n tally o n m etal ro llin g shelves w it h in the vault.A b o u t 3 00 nineteenth and twentieth century full-leather spring-b ack stationers' bindings, m any covered in protective w hite canvas jackets, were un to uch ed by the fire but im pregnated w ith a layer o f soot and reeked o f sm oke.Front of the Sevier County Recorders Office (Richfield, Utah, USA) on May 9,2006, one week after the fire.Photo credit Randy Silverman The Problem A m o n g U .S .co m m e rcia l disaster firm s, the cu rre n t stand ard for rem o vin g soot's residue from books is to w ipe dow n the covers w ith a "chem ical," or natural rubber sponge,2 and then "ozonate" the books to elim in ate the residual sm oky odor.T h is approach leaves m u ch to be desired.W h ile the sponge traps m u ch o f the fine, carbon-laden particulate in its tan, rubbery surface, it also quickly fills w ith residue.Recovery workers m ust constantly rotate their sponges to A m o n g U.S.

Fireexpose unused areas to the grim e and discard spent sponges as they are not readily cleaned. T h e w ip in g process forces som e o f the fine, d a rk soot particles b ack in to the interstices o f the m aterial being cleaned, especially w hen that surface is as porous as the open weave o f canvas book jackets. Trapped soot becomes m ore intractable w ith tim e as the polym erized and dehydroge nized byproducts o f the fire chem ically bond to their surroundings. 3 T h e friction o f w ip in g also causes som e portion o f the sponges soft rubber to transferthe second phase o f this cleanu p in c lu d e d m e ch a n ica lly w ip in g the b o o k s surface w ith rubber sponges or Webril® W ip es (a nonwoven 1 0 0 % cotton pad used in the printing industry for non-abrasive cleaning o f p rinting plates). 5 E
to the books surface, trading one unstable residue for another.4Finally, exposing "cleaned" books to ozone to reduce the residual sm oke odor causes further degra dation.A strong oxidizer, ozone aggressively breaks dow n paper, cloth, leather and adhesives w h ile it decomposes the organic com ponents o f the smoke-a hig hly undesirable tradeoff for books o f historic significance m andated by law to be m aintained in perpetuity.I n short, soot is an extremely tenacious mate rial to remove.U n lik e dust, it is a solid/liquid residue com posed o f carbon suspended in an An interior office with evidence of smoke damage on the walls.Photo credit: Randy Silverman oily foundation o f partially consum ed com bus tion byproducts.T h e carbon w ith in these tar droplets is so fine that it is readily dispersed by the "pressure and buoyancy created b y the heat o f the fire" and aerodynam ic conditions such as "stack effect, w in d pressures, the b uilding geom etry and its barriers (such as walls and floors), and ventilation practices."5Soots fine powder coats every exposed surface, penetrating even the tiniest crevices and crannies, anchoring the carbon w ith o ily tars w here it lands.Rem oval attem pts by w ip in g , even w ith an absorbent, fleshy m aterial such as a natural rubber sponge, sm ears w hatever soot does n o t b o n d to the sponge, com p ressing an d em b ed d in g the dim inutive, greasy specks further into the sur face and m aking them m ore difficult to remove.A s soot ages, it ch e m ica lly cross-links to the m aterial it is in contact w ith , m aking im m ediate cleanup the optim al course o f choice.V acu u m in g w ith a H E P A filter in tandem w ith m anual w ip in g can help, but alone it is a ctu a lly less effective than w ip in g w ith an absorbent m aterial.In the 1997 Saskatchewan M useum fire, Spafford-Ricci and G rah am report the soot removal protocol used for book cleaning included an initial vacuum ing o f the books binding, followed by a separate vacuum ing o f the text block.C a re was taken not to touch the surface o f the books w ith the vacuum s nozzle as this contact w o u ld push soot into the woven fabric o f the bookbindings.A fter vacuum ing, lim in a t in g resid ual sm oke od or from objects fo llo w in g soot rem oval is the next p ro b le m .I n ad d itio n to sp rayin g scents to m ask the odor, three approaches p red om inate w it h in the fire recovery in d u stry : ch e m ica l d eod orizing , th erm al d eo d o rizin g an d ozone treatm ent.U n fo rtu n a te ly, all have serious d raw b acks w h e n d ealing w ith cu ltu ra l h e r itage m aterial.Record book storage vault with metal roller shelving; a temporary positive air ventilation system is set up to help with soot extraction.Photo credit: Randy Silverman C h e m ica l deodorizing eliminates odors through a chem ical reaction occurring w hen the chem ical fumes o f the product com e into contact w ith sm oke residue.Th e se deodorizers co m e in a w id e range o f extrem ely p ung ent fragrances designed to "purify" air spaces rang ing in size from 1,0 0 0 -2 0 ,0 0 0 cubic feet.T h e long-term effects on cultural property o f these proprietary formulations have not been analyzed.M o re b ro a d ly however, h a rm fu l effects from gaseous p o llu ta n ts -p a rt ic u la rly s u lp h to elim in ate vo latile organic co m p o u n d s ( V O C s ) from the am b ie n t air.E sse n tially the system is an afterburner that draw s w orkp lace air through a com b ustion ch a m b e r w here V O C s are in c in e ra te d .8M o s tly used in in d u stria l settings to deal w ith gaseous byproducts from petrochemicals, printing , p aint, food, sewage and waste treat m ent, application o f this technology to reduce sm oke odors from heritage m aterials has not yet, to m y know ledge, been attem pted.F in a lly ozone is co m m o n ly used to treat sm oke odors in affected household and office objects.T h is treatm ent in clu d es creating copious am ounts o f 0 3 w ith an electric ozone generator and sequestering the sm okedam aged m aterial in a co n fin e d space w ith the gas.U n fo rtu n a te ly w h ile 0 3 elim inates sm oke odors, in h ig h co n ce n tratio n s 0 3 is b oth h a rm fu l to h u m a n health9 an d an aggressive o xid izer k n o w n to h arm a w id e range o f c u ltu ra l heritage m aterials, as noted ab ove.10 H e n c e , despite its co m m o n use for less significant objects, 0 3 should be avoided.A t present, the o n ly safe ap p roach to remove sm oke odors from cultural m aterial is to isolate objects in a room w ith an operating air p u rific a tio n system c o n ta in in g activated carb on , zeolite an d /or p otassium p erm an ganate filtration.C o n tin u o u sly re-circulating filtered air past the objects w ill g rad u ally reduce sm okes lingering odor i f the m aterial can be w ell exposed to the air flow.A n inex C hem ical deodorizing eliminates odors thro u g h a chem ical reaction occurring when the chem ical f a n e s o f the p ro d u ct come into contact w ith smoke residue.

Firegenerator w in d in g s an d transform ers; and rem ed iating m o ld from b u ild in g in te rio rs. 13 T h e system is p ortab le an d can be pow ered b y an electric generator, ad d in g sig n ifican tly to its merits since the C o u n ty Recorder w ould n o t p e rmT h e se m u ltip le forces-co n tractio n due to co ld , tu rb u le n ce caused by rap id su b lim a tio n and pressure from the compressed air stream- o ccu r sim ultan eously. A s the m in u te d ry ice particles penetrate the interstices o f the mlines run w ith a roll) presented no problem in the cleaning, suggesting that m od em titling on mass m arket books is far m ore friable than earlier hand w ork. Sim ilarly, direct ing the d ry ice nozzle directly at the edges o f the text could abrade the paper surface slightly, so the situation was remedied b y focusing the nozzles aim specifically at the board edge so o n ly
Photo credit Randy Silverman

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No secondary waste • Safe for the environment • Safe for employees • Safe for end products • Safe for equipment We then co m p a red dry ice blasting w ith tw o other fo r m s o f soot rem o va l u sin g a c tu a l record books; w ip in g d o w n p a r t o f a book w ith a n a tu ra l ru b b er sponge a n d v a c u u m in g another section w ith a H E P A filter.

Fire
Photo credit: Randy Silverman

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more information or to arrange a free CoLibri Cover sample on your book contact us at 800-526-5640 or custserv@archival.com.a r c h i v a l .c o m Division of Library Binding Service LBS/Archival Products 1801 Thompson Avc.P.O.Box 1413 Des Moines, Iowa 50306-1413 1-800-526-5640 515-262-3191 Fax 888-220-2397 custsc rv@arch ival.com