Protecting precious art with UV glass bonding
A priceless collection of Chinese artifacts in the entrance of Khotan, a newly remodeled high end Pan-Asian restaurant at Treasure Island Resort Casino,Las Vegas. Glass display cubes by: glass contractor Elite Glass & Mirror, Las Vegas; glass supplier Oldcastle Glass, Los Angeles; UV glass bonding technology and supplies provider C.R. Laurence Co., Los Angeles
When the management of the Treasure Island Resort Casino in Las Vegas recently acquired a priceless collection of Chinese artifacts to adorn the entrance of Khotan, their newly remodeled high-end Pan-Asian restaurant, they had three concerns: protection of the articles from casual contact, security against theft or vandalism, and how to achieve these goals while effectively showcasing the intricate beauty of the pieces. The artifacts consisted of two 1,200-pound Manchu Dynasty solid jade vases, one exquisitely detailed nephrite jade stallion and one 35,000-year-old mammoth tusk decorated with intricate carving dating back to the 18th century AD.
A procedure in pictures
Click here to access a photo gallery documenting the project
As a regular contractor for Treasure Island, Charlie Dycus, owner of Elite Glass & Mirror in North Las Vegas, was asked to come up with a display solution that would cover all three of management’s main concerns, quickly. The solution: five-sided display cubes made of 3/4-inch, laminated PPG low-iron Starphire glass with thin bond UV adhesives. The four cubes would weigh from 396 pounds to 725 pounds, secured by pins that went through the glass and locked into the pedestal base.
Facing a tight deadline, Dycus assembled his crew of glass craftsmen with UV bonding technicians and supplies from C.R. Laurence Co. on a Saturday morning to commence assembly of the display cubes. Although they originally assumed they could complete the project in a single day, it was two and a half days before the cubes were ready for delivery and final assembly. While the technical procedures for UV bonding are fairly simple--clean, heat, apply and cure--the logistics of handling pieces of 3/4-inch laminated glass and partially assembled structures around when each piece of glass adds more than 100 pounds to the end result complicated matters.
Normally, the UV adhesive of choice for a laminated glass project would be a formula with some elasticity in the finished joints. But in this case, high tensile strength was more important in the long run. So, the team used a medium viscosity adhesive that would yield tensile strength of nearly 4,000 psi at full cure.
Construction of each cube began with a wide face lite lying flat on the work table, with narrower end lite edges adhered to the surface. The second face lite was then attached across the two end lites. All the edges were aligned so that the top corners were perfectly flat and square to receive the final top lite. Any dimensional variance was kept to the bottom of the cube. After completing this preliminary assembly, the cube was carefully tipped off the assembly table onto a specially designed transport base. Once in the upright position, the top cap was attached and secured in place.
The UV adhesive, when applied liberally to eliminate air bubbles, acts more like 40 weight motor oil than an adhesive; parts easily shift out of position. As a result, the techicians quickly learned to have all the cups, clamps and fixation devices in place before applying the adhesive bead and setting the glass into position. Using carpenter squares to check top alignment and the 90-degree assembly angle, two men still had to hold the panel in position while the initial 15-second pre-cure illumination was applied to both sides of the joint.
Another tradeoff when using excessive amounts of adhesive is the added clean-up required. The majority of the excess can be soaked up after the glass is first set; however, this added step is time consuming and usually not necessary.
Laminated glass is normally cured using visible and UV light, since the PVB layer acts as a barrier to UV radiation. In this case, the cubes incorporated 3/8-inch low-iron ultra-clear glass on each side of the PVB layer, so the technicians duplicated the standard UV exposure process, illuminating both sides of the bond joint. Using two powerful CRL XX40 UV lamps held end to end, the outside was set cured for 15 seconds. The lamps were then moved to the inside for another 15-second set. Since UV adhesive cures from the center outward, all excess adhesive could now be cleaned from the outside of the bond. The lamps were then moved to the outside again for a full set illumination of three minutes. At this stage, all clamps and fixation devices were removed and the inside of the joint was thoroughly cleaned. The final step involved a three-minute illumination of the inside surfaces. This procedure, creating bonds with strength exceeding that of the glass itself, was repeated for the balance of the project.
To safely transport the cubes from the Elite Glass & Mirror facility in North Las Vegas to the Treasure Island jobsite, the team constructed special heavy-framed forklift pallets. These pallets were designed to cushion and restrain the cubes, and featured an open bottom allowing access into the cube. This access space allowed the cubes to be lowered by forklift over the lucky person chosen to perform the final illumination and cleaning of the top lites.
Well before sunrise Wednesday morning, Charlie and his crew gathered at Treasure Island with a forklift, forklift boom and a pair of Wood’s Powr-Grip MRT Vacuum Lifting Frames. As each artifact was mated to its steel-reinforced display pedestal and cleaned one last time, the corresponding glass cube was also meticulously cleaned inside and out. The MRT lifting units were hung from either the forks or the forklift boom, depending on the spacing required, and carefully adjusted to make sure the cubes would be lifted straight up with no tipping or swinging. Since all the clearance tolerances from glass-to-object were measured to the inch, and the glass-to-pedestal tolerance was down to 1/16 inch, it was imperative that each cube be hung perfectly plumb and square before being lowered onto its pedestal.
The three smaller displays were assembled inside the casino area by rolling the forklift forward and lowering the cubes onto their pedestals. The combined height of the largest cube / pedestal display and the forklift mast required that this operation be moved into the hotel registration area, which offered higher ceiling clearance. This large display was assembled by lifting the cube straight up and then rolling the pedestal and artifact forward. The cube was then lowered onto the base. Since the pedestals had been fabricated combining casters and jack bolts into the steel framework, it was possible to then roll the finished display back into the casino area.
The success of the project could be measured by the satisfaction of the Treasure Island management team. Their priceless collection was now safely secure within a shield of crystal clear glass.
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