15,000 GRANITE SLABS JOURNEY TO MIDTOWN

755-9040. By PAULA DEITZ

When a flatbed truck pulled up to the International Business Machines Corporation's tower site at 57th Street and Madison Avenue not long ago, its arrival signaled a new stage of construction. The truck's cargo contained two gleaming granite panels. They were the very first delivery of the prefabricated gray-green panels that will alternate with green-tinted glass to form the facade of the 43-story I.B.M. tower.

The arrival of this granite heralded the end of a dramatic journey that began at a mountainside quarry in a wilderness area north of Quebec City. Hundreds of tons of it have already been carved out of a mountain in Portneuf Provincial Park and transported by truck to the LaCroix factory in the French-Canadian village of St.-Sebastien, southeast of Quebec City, where the stone was cut and polished. Finally, truckloads of it have been transported four times a week to Hauppauge, L.I., to the Hohmann & Barnard Company, where it is being assembled, eight slabs to a steel truss.

In the early design stages, the architect, Edward Larrabee Barnes, said granite was but one of the materials being considered for the facade, along with glass, aluminum and steel. Stone, which at first seemed costly in comparison, became a viable solution when the sudden increase in energy costs to manufacture the other products made them as expensive. But cost was only one factor.

''In combination with a green glass, another mineral substance, there is a pleasing unity and human scale that is lost in a mirrored surface,'' Mr. Barnes said.

Selecting a material and its color is not of simple consequence. The material will be highly visible in midtown Manhattan on an important crossroad, as if a mountain had been dismantled, polished up and reassembled in midtown. Before the tower is completed in 1982, I.B.M. will have spent $8 million on granite.

For the I.B.M. tower, Mr. Barnes specified the gray-green granite because it would blend in with the nearby Corning Glass Company's green glass building and the projected greenhouse park on the I.B.M. tower's south side.

In their search for a suitable gray-green, the architectural staff traveled around the United States to study buildings faced in green granites from many different countries, including Norway and Czechoslovakia, and they found such variables as a high iron content in boulders from Africa that turns it yellow as it rusts.

Because darker granites are more expensive, another consideration was the waste factor; that is, to acquire the necessary 270,000 square feet - or approximately 15,000 stones in mostly 5-by-4-feet slabs, three inches thick, of uniform appearance - how much of the granite quarried would go to waste.

To reduce the waste factor, the architects had already reduced the original 5-by-8 size, or four stones to a truss, to 5 by 4, or eight stones to a truss, the smaller stones being easier to obtain with less waste.

Another questions was: once the quarry operation began, would there be enough stone? Green granite, used generally for decorative details, is not usually excavated in a quantity required for a skyscraper.

On decision day in 1978, two trusses were set up facing the sun, each with the granite of one of the two final contenders in a yard owned by the general contractor, the Turner Construction Company, in Carlstadt, N.J.

A highly polished, self-cleaning finish on the granite had been specified; and angled to the southeast the slabs were gleaming in the sun that fall day when Mr. Barnes and his wife Mary, an interior designer who helps with the selection of the materials, arrived to make the choice.

The choice was narrowed down between an upstate New York granite, a variation of pale greens and grays that would give a random design to the exterior, and one from Quebec with a uniform mottled appearance.

The Barneses made several trips to the yard before making the final decision in favor of the Atlantic green granite from Canada, which had been submitted by a New York stone contractor, Peter Bratti Associates in New York. Based on the samples submitted, specifications of acceptability were put into writing by the architect.

But the testing was still not over. To make a determination on questions of performance, Mr. Barnes called in Charles Fairhurst, head of the Department of Civil and Mineral Engineering at the University of Minnesota. The granite was tested for ''weathering''; that is, how it would withstand the freeze-thaw process as well as exposure to chemicals.

Dr. Fairhurst also took many core samples at several locations deep in the quarry. These were sliced and polished; and by comparing them to the desired color, the LaCroix concern had precise indications where to go for the best stone.

The architect's office hired James Rappa, a young American sculptor who has worked in stone, to oversee the selection of the stone. Since 1979 he has been working in the LaCroix plant at St.-Sebastien, the French-Canadian village that is the headquarters of the LaCroix family, about 100 miles southeast of Quebec City and 35 miles from the Maine border.

This area of Canada is one of quiet little farm towns with houses and silos set right by the road. Occasional signs on trucks and buildings such as ''Frontenac Granit,'' or ''St.-Samuel Granit,'' announced this as granite country. The LaCroix plant is a long low structure on the outskirts of the village.

A. LaCroix et Fils was founded in 1962 by Armand LaCroix Sr., now in his 70's. Today his sons - Claude, Jean-Marc, Yoland, Paul-Andre and Rejean - run it.

In the little anteroom that serves as a company office, architectural drawings for the I.B.M. curtain wall were spread over every surface.

Right now, supplying the I.B.M. Tower is the LaCroix brothers' total occupation. To ''mobilize'' for the I.B.M. job, a new plant was built over their old one, which was then dismantled in the process, and new machinery was purchased.

Claude LaCroix put on his galoshes, and opened the door into the main plant, which is divided into two major areas, one for cutting the blocks, and the other for polishing and trimming the slabs, as well as packing them.

The locale may be Canadian but the process is Italian. Most of the new machinery purchased for this commission is made by the Zambon Company of Vicenza. In the cutting room, a tall hoist dangled the granite from cables as it lifted the blocks stacked in the rear and placed them on cutting platforms. There a 12-foot-high, one-blade Mercury circular saw with diamond teeth cuts through the blocks.

A constant spray of water, hence the galoshes, keeps down the level of granite dust, something the brothers fear since their father is suffering the advanced stages of silicosis, having worked in quarries and around granite since he was a boy.

Once the boulder size blocks are sliced into three-inch slabs - 23 to a block according to one count - the slabs are broken loose from the base and allowed to fall on a rubber tire; the rough edge is removed with a chisel. From there the flat slabs are rolled to the automatic polishers, a series of five table-like machines, each with a mechanical arm over it that holds a brick of abrasive material that polishes the granite's surface and that is of a progressively finer grade from one polisher to the next. At the last, a solution of tin oxide and water is washed over the stone while it is polished with a piece of lead wrapped in felt.

At the end of this approximately 25-minute process, the gleaming slabs arrive at Mr. Rappa's station at the factory. He has mounted three sample stones in an upright position: one of the approved color and the other two, disapproved, either because the stone is too gray or too yellow. The new stone is compared under lights of 1,500 watts each. Once he accepts it, he initials the back of the stone ''JR'' in yellow paint and grades it I, II, or III. If unacceptable, he marks it with a ''pas bon,'' French for ''not good.'' With the same paint he outlines on the face of the good stones the area that may be used.

The acceptable slabs are trimmed and the edges are polished. Finally four holes are drilled into the ends for the insertion of a steel plug. A three-inch threaded rod known as a stud is screwed into the hole from the back of the stone and will eventually be connected to a truss. The holes are then refilled with an epoxy.

The finished slabs are arranged in stacks of six and grouped by the assigned letters A, B or C to indicate which edges have been polished. This determines the position on the truss. The stacks are bound with steel bands and shipped out by truck to the plant on Long Island.

The quarry is a four-hour drive from the factory on the other side of the St. Lawrence River, in the little town of Riviere-a-Pierre. Several large granite companies are located there , and the streets are lined with small ranch-style houses that look more like banks, clad as they are in a local gray granite. The town forms the entrance to the provincial park, Reserve Portneuf, and it is in this park, on government-owned land, that the LaCroix brothers have obtained the rights to quarry the Atlantic green granite.

Only six men work at the quarry, including the crane operator who operates the boom that rotates around a tall mast riveted to the ground and radially stayed by guy wires that give it the appearance of a giant May pole. The granite blocks swing quite low as they are brought to the base of the hill for loading onto trucks.

The natural cracks and joints of a quarry dictate the direction for cutting stone as well as the size of the block. In some cases, several spikes are driven simultaneously with steel wedges. Another method is to use black explosive powder that releases a gas that fractures the granite horizontally. A flame torch is used for cutting a vertical channel. In freezing weather cracks can be filled with water and the expanding ice cracks the stone.

As the blocks of stone are removed, they are marked ''I.B.M.'' with a number indicating their position in the quarry for future reverence. As the stones are processed, the LaCroixbrothers can keep track of the areas that produce better stones than others.

''Before the company's rapid evolution in the 70's, fabricating granite for curtain-wall construction, the business had been expanding only moderately,'' Claude LaCroix explained. ''We were cutting stone for such projects as the outdoor steps that lead up to churches' entrance areas for hospitals and rusticated facades for houses.''

The plant where the granite slabs are transported, Hohmann & Barnard Inc., is located in an industrial park in Hauppauge, L.I. This is no local company, for, one soon learns from Ronald Hohmann, the company has been involved in assembling metal accessories for construction as far away as the main terminal building at Jeddah International Airport in Saudi Arabia.

The Bratti Company maintains a small trailer office on the premises where hanging on the wall was a drawing of the west elevation of the I.B.M. tower with two rectangular areas colored red on the sixth and seventh floors. Written in large letters was this message: ''Two panels set, 1745 to go'' alluding to the first delivery and installation. By now, there have been many more deliveries and half the granite has been installed.

Right now, the assembled panels are standing in orderly rows like upright dominoes covering a two-and-a-half acre yard behind the plant.

One of the advantages of prefabricated panels, as opposed to installation at the site, is that there is more quality control and less damage to the face of the stone. It is also faster because eight stones are attached to the frame known as a truss. The assembly weighing three-and-a-half tons goes up at once.

The steel truss is a rectangular form 7 1/2 feet high that will extend the width from column to column about 19 feet. This allows space at the column joints for a window-washing track.

All of the fabrication, drilling and welding of the trusses is done in the Hohmann & Barnard shop, after which the steel frames are taken outside for sandblasting. This jet of sand from a hose removes rust from the trusses.

After a coat of zinc-rich primer, they are spray-painted with that rust-proof red Epoxy paint called Tnemec (cement spelled backward). Each stone is bolted to the truss by the four studs embedded in it, and rests on two steel shelf angles. All of these connections are made of a rustproof nonmagnetic stainless steel. Once a Styrofoam backer rod, which makes the joints resilient, is in place between the stones, they will be sealed. A sheet of boardlike water-resistant insulatory material, called Thermafiber, is hooked onto the truss behind the stones and the whole is protected by a galvanized backplate, also painted with Tnemec.

The truss is hooked onto the tower's frame like a curtain, hence the term, curtain wall. Two gravity supports, one at either end, take the entire weight assembly.

Soon the I.B.M. tower will be the only building in the world clad entirely in the Atlantic green granite from that particular quarry. Except, that is, for Claude LaCroix's village house, which he has faced with slabs of the same polished granite.

Paula Deitz is co-editor of The Hudson Review.