Before leaping into Winchell's report on the weathering of the stone, I have one more quote from the time of the finding of the stone, this as recorded in Whalgren's book, and are also from a Chicago newspaper to whom Curme had apparantly given an interview:

"The letters were evidently cut by some one not a novice, for although they have an irregular appearance a close observation shows that the lines are almost as true as those on a modern tombstone, though the roughness caused by the implement used in cutting has not been smoothed and covered as in the inscriptions of today.
The most positive proof that the inscription is not ot the ancient origin claimed by its discoverers is the fact the the crevases which form the letters are of a lighter color than the outer surface of the stone; this could hardly be the case if the stone had been buried for the 600 years that must have elapsed provided the inscription is authentic.'
Professeor Curme is in doubt about 1362 being the exact date of the stone. The last line of the inscription was cut through a portion of the cement surrounding the base, an dthe letters and figures cannot be clearly distinguised, the cement having been chipped away. This cement also throws a doubt on the origin of the tablet, for if it was place there by the Norsement mentioned in its story they must necessarily have waited a week for it to dry before the last line could have been cut through it" (The Daily Inter Ocean - March 1, 1899)

This is the only mention of cement that I have found. Perhaps this is a mistake for the calcite deposits on the stone (see Winchell below) which show a greater amount of weathering than the greaywacke of the stone. I can come up with no other explaination of this statement (I can see no reason either a hoaxer or a Norseman would have had cause to use cement on the stone)
It should also be noted that Curme pointed out in the Skandinaven article posted previously, that the inscription had been scratched out after the stone was unearthed, and that "wherever the characters of the inscription have not been disturbed, they have precisely the same color as the general surface of the stone." Winchell also notes that the runes had been scraped with an iron nail (see below)

It has been frequently pointed out how clear the runes are, which seems at odds with the assumed age of the inscription. Professor Flom, for instance says in 1910 that the

"smooth surface of the stone which gives it the appearance of having been shaped and chiseled in recent times... and the perfectly distinct runes themselves; so different from the character of genuine old inscriptions" (Whalgren p 66)

"It is graywacke, of dark gray color, evidently rifted from some large boulder of glacial drift, which forms the surface of al the region. On the reverse face, opposite to the face bearing the longer inscription, are sever glacial striae, or scratches and gouge-marks, worn in the stone by its rasping with other drift boulders or pebbles while being carried forward by the ice movement. These markings are very clear cut and have been perfectly preserved during the 7,000 to 10,000 years since the Ice Age. Hence no surprise or reason for distrust is occasioned by the excellent preservation and unweathered condition of the rune characters." (Records of the Past Vol IX Part I January-February 1910 p4-6)

"When we compare the excellent preservation of the glacial scratches, shown on the back of the stone, which were made several thousand years ago, with the mellow, time worn appearance o fthe face of the inscription, the conclusion is inevitable tht this inscription must have been carved many hundred years ago" (Journal of American History, 1910, IV, 180 - quoted by Holland "Westward From Vinland" p 130)

"It may be assumed that, if this stone was erected, as it claims, by explorers in 1362, it was set up on end, and that the lower end, where no runes are engraved, was buried in the ground. When it was found, according to the testimony of Mr. Ohman, its inscribed face was downward. Now the lower end of the stone is not cut off squarely, but is roughly beveled on one side. Gravitation alone acting on a beveled stone would cause the base to be diverted to one side, in the same manner as a single beveled stake when driven into the ground. In setting inot to the ground, owing to the direction of the bevel, this stone naturally would fall with its face side upward. Its position, therefore was determined by some other force than gravitation. either it was purposely placed with its rune inscription down, which in not reasonable to suppose, whatever its age, or it was acted on by some other force which caused it to fall over forward. We cannot of course state how many forests have grown and been thrown down by tornadoes within the 548 years through wich it may have been in the spot; nor how many forest fires have devastated the region; nor how many buffaloes have rubbed against it; nor, finally to what acts of violence the native Indians may have resorted to counteract its evil influences.
Numerous works of the mound-buildeing Indians are known in the immediate neighborhood, and they certainsly would have discovered the monument. If they participated in the massacre of the ten ment at the camp, they would quite certainly look upon the stone as a retributive threatening reminder o ftheir pale-face victims.

The interior of the stone is dark or dark gray. On close inspection it can be seen to contain many grains of quartz which are roundish, showing a sedimentary detrital origin. In a thin-section prepared for microscopic examination, it show not only rounded quartz grains but also feldspqr grains, and a finer matrix consisting chiefly of quartz and biotite. The dark color of the stone is due to much bitite, mainly, but also to an isotropic green mineral (chlorite?), magnetite and hematite. The quartz has become mainly re-formed by secondary growths. There is a crypto-gnessic elongation prevalent in the mica, and also to some extent in the larger quartzes. The weathered surface is somewhat lighter, and yet it is firm and wholly intact. It is evident that the surface color has been acquired since the Glacial period, and therefore that some 7,000 or 8,000 years may have elapsed since its face was first exposed to the elements. The reverse of the inscribed side is more alterd by weathering and carries evident older glacial striations.

The first impression derived form the inscription is that it is of recent date, and not 546 years old. The edges an dangles of the chiseling are sharp and show no apparent alteration by weathering. The powder ofthe stone when crushed is nearly white. None of this powder is preserved in the runes on the face of the stone, and it is necessary threfore to allow it some years of age, but iti is quite impossible to draw a decisive inference of the age of the inscription from that alone.
The edge of the stone differs in this respect from the face, since most of the rune letters show the white powedr formed by crushing the stone. the difference was said to be due to the fact that the runes on the edge had been filled with mud and had been cleaned out by scraping them with an iron nail. Indeed, in the runes in some places on the edge can be seen with a pocked magnifier smal quantities of fresh metallic iron evidently dreived from that process.
The freedom of the face of the stone from glacial marking is to be noted. It seems probable that the smooth jointage surface on which the inscription is made was of a more recent date than 7,000 or 8,000 years.

It is plain that the calcite deposit the covers a part of it was formed in a joint-opening before the stone was seperated from its neighbor, and that it has had approximately as long direct exposure to the elements as the rest of that surface. The well preserved condition of this calcite, as a whole, not less than the non-glaciation of the face of the stone, indicates a period of exposure less than 7,000 or 8,000 years. Marble slabs in graveyards in New England are more deeply disintegrated than this calcite, when they stand above the surface of the ground. The immediate surface of the calcite, especially the edges formed by cutting the runes, is smoothed by recent friction of some kind, much more than the surface of the graywacke; and this is attributable to wearing away when the stone served as a stepping stone at the granary. If the engraved face of this stone was seperated from its neighbor since the Glacial age, as seems certain, it must have been in some way protected from the action of the elements; and consequently this calcite is comparable wth the white, fine grained limestone boulders and pebbles that are common in the body of the drift in that part of the state. Such boulders when freshly taken from the till in dep excavations ar not rotted, but are fresh and firm and smooth as marbles, and show distinctly the fine glacial scratches which they received during the Ice age, which ended about 7,000 or 8,000 years ago. When, however they are found exposed at the surface of the ground, they have lost this smoothness and all the glacial marking, and their surfaces afford a fine white powder of natural disintegration. As there is nothing on this calcite (which is also the principal ingredient of the limestone boulders), it is evident tht either the calcite has but recently been exposed or has been protected from the weather. If the slab was seperated from its neighbor 548 years ago, it must have lain with its face side down during the most of that period, and if seperated earlier it must have been covered with drift clay. If it was seperated fifteen or thirty years ago, it may have lain with its face side up and probably would show no more weathering than it now evinces. In short, there is no possible natural way to preserve the calcite scale from general disintegration for 548 years except to bury it beneath the surface. If it were not thus buried and still is intact, it must have been exposed and the inscription must have been made less than a hundre years ago, an d probably less than thirty years ago.

The general "mellow" color of the stone, is also to be noted. This is the first apparent effect of weathering. Graywacke may be estimated to be fifty to a hundred times more durable in weather than calcite, some graywackes being more resistant than others.
There are six stages of the weathering of graywacke exhibited by the stone, and thy may be arranged approximately in a scale as follows:

1. A fresh break or cut --- 0
2. Break or cut shown by the runes of the face --- 5
3. Edge face, which has not been engraved, but was apparently dressed by a rough bush-hammering --- 5
4. The inscribed face of the stone --- 10
5. The finely glaciated and polished back side and the non-hammered portion of the edge --- 80
6. The coarse gouging and the general beveling and deepest weathering of the back side --- 250 or 500

These figures are but rough estimates and are intended to express the grand epochs of time through which the stone has passed since it started from the solid rock of which it formed a part prior to the Glacial perioid; and to a certain dgree they are subject to the errors fo the personal equation of the person who gives them. Prof. W O Hotchkiss, state geologist of Wisconsin estimated that the time since the runes were inscribed is "at least 50 to 100 years." If the figures in the forgoing series be all multiplyied by 100 they would stand:

(1) 000: (2) 500: (3) 500: (4) 1,000: (5) 8,000: (6) 25,000 or 50,000

Since 8,000 years is approximately the date of the end of the latest glaciation (5), the numbers may be all acepted as the approxiamte number of years required for the various stages of weathering. Hence stages (2) and (3) may have required each about 500 years.

The composition of the stone makes it one of the most durable in nature, equalling granite, and almost equalling the dense quartzyte of the pipestone quarry in the southwestern part of Minnesota. On the surface of this quartzyte, even where exposed to the weather since they were formed, the fine glacial scratches and polishing are well preserved, and when covered by drift clay, they seem not to have changed at all."

Summary and comments
1) Winchell does not seem here to be the fanatical supporter of the stone that many detractors paint him as. He admits to the fact that he may be in error in his calcualtions, and the calcite weathering is certainly less than 500 years.
2) The desintigration of the calcite, according to Winchell would have requiered approximately 15-30 years. Conceivably, such weathering could have occured in the 10 interval after its discovery, but this is unlikely, especially if it was not exposed to the elements. The stone must have been burried for much of its existance or there would have been a greater disintegration. It is unlikely that it could have been unearthed by natural means; if a hoax, it could have been dug up by a farmer in his feild and left to one side for 15 years before our hoaxers decided to inscribe and bury it. Or it could have been inscribed (such as by the Noirsemen) and knocked over by some outside force 15-30 years after the posting. However, the calcite evidence shows that it could not have been unearthed, inscribed and immediately reburried as many hoaxologists (hoaxologists? is that a word?) claim - there would have been no time for the calcite to disintegrate.
3) Winchell compares the weathering of the inscription to other weathering signs on the stone, and estimates that it occured in 1/16th of the time of the glacial striations. As the Ice Age in Minnesota ended about 8,000 years ago (when the striations would have been grooved into the rock), the inscriptions would have been incised approximately 500 years ago. Winchell does leave plenty of room for error, however even if he were off by a factor of 10, then it would still have been fifty years (1860) since the insription was inscised (and note that this is the absolute minimum time given by Hotchkiss. This still places it before the general settlement of the land, and severly limits the possibility of a hoax. Lest we get too caught up in this, please remeber that Winchell's official estimation was indeed about 500 years.
4) The hardness of the graywacke, its comparison to granite and quartzyte, and the minimal weathering of the 8,000 year old glacial striations, show that any denunciation of the stone based on the apparent newness of the inscription is a false lead.

Other Stuff:
A more complete quote from Hotchkiss (partially quoted in Winchell) is as follows:

"I have carefully examined the various phases of weathering on the Kensington Stone, and with all respect for the opinioins of philologists, I am persuaded tht the inscription cannot have been made in recent years. It must have been made at least fifty to a hundred years ago and perhaps earlier" (quoted in Holland "Westward from Vinland" p 130 -statement on file in MN Hist. Soc.)

Also in Holland's "Holy Mission to Minnesota..." he writes:

"As an offset to this evidence Dr. Brondsted in 1948 called attention to an H which I in 1908 carved on the lower end of the stone as a future check on the weathering process. He says that this carving shows a beginning of weathering (en begyndende forvitringshud). Then he reasons: 'if it takes 40 years to produce a light patina, one may well conclude that a full patina could be produced in a perioid of 70-80 years, an dthe evidence claimed in the patina is no evidence at all' ".
(Quote from Bronsted from "Problemet Om Nordboer I Nordamerika for Columbus'" p 71)