PREPARING CROSS COUNTRY SKI BASES
When the season ends, the ideal treatment for ski bases is to iron a layer of wax onto the glide surfaces and then leave this thin layer on the bases all summer.Waxable diagonal stride skis should have any kick wax or klister cleaned off, then 2 or 3 layers of either green kick wax or binder wax applied to the kick zone. A paste wax (like F4 from Swix) should be applied to the kick zones ("fishscale" area) of no-wax skis. Ideally, the skis are also kept in a cool location.
The purpose of summer waxing is to prevent the plastic bases of the skis from "oxidizing" and drying out. Technically what happens is that the plasticizers - the compounds that make plastic "plastic" - can evaporate from an unprotected base. A good illustration of this is the plastic dash of a car. As the dash oxidizes, the plasticizers become volatile, dissipate into the air (often forming a film on the inside of the windshield), leaving behind a surface that looks dull, even powdery.
Ski bases have been developed to be very hard, yet at the same time very porous. When skis are glide waxed, the hot molten wax literally drops into the pores of the ski base. By simply changing the type of wax in the pores of a ski base, the ski can give optimum glide in a variety of snow conditions. These pores are actually a network of open areas in and around very fine strands of plastic. When the surface layer of the base becomes oxidized, not only does the plastic become less slippery, but it also becomes harder for wax to penetrate into the ski. The net effect is that the ski does not glide as well and the application of wax will probably yield little improvement because the wax simply isn't going into the base.
The ideal world and the real world are seldom in sync. Most skis seldom get a coat of summer wax. They probably also don't get waxed often enough during the ski season and in general could use at least an annual overhaul. As a general rule, unless skis have been protected during the summer with a layer of wax, they will need to have the bases re-prepared. During ski season, skis that are periodically waxed (at least every 100 km or so - it depends on the abrasiveness of the snow) probably do not need any additional care except for waxing.
Base preparation consists of three basic steps: peeling the base to remove any oxidized layer, applying structure, and finally re-waxing. The basic tools required for "peeling" are first and foremost some sort of "profile" bench that supports the entire length of the ski, plus a very sharp steel scraper.
Good profile benches are not inexpensive (starting at about $100). The most important quality is a method, usually a clamp of some sort, that securely holds the ski in place while the bench supports the ski along it's entire length.
SHARPENING STEEL SCRAPERS (Return to top)
At SIERRA NORDIC, our preferred steel scrapers are the thin ones made by Sandvik for fine woodworking. Keep the steel scraper sharp by drawing it across a mill bastard file. Place the file on a bench and pull the scraper (held vertical, perpendicular to the file) across the file. Don't put the scraper in a vise and try to file it - that method doesn't work as well. Draw the scraper a couple of times (one way) across the file, then turn it around and draw it the other way. Use either a 10 or 12 inch file (without a handle so that it can lay flat on the bench). A mill bastard file has its "teeth" cut with a slant in one direction, so only file in one way (towards the handle), not back and forth. Use light pressure and sharpen the scraper often (even 2-3 times per ski).
BURNISHING THE EDGE (Return to top)
The edge of the steel scraper should now be "burnished", meaning that the edge is rolled over slightly by pushing on the corner of the edge with a forceful polishing type action. Essentially what the filing did was make for a sharp 90º angle between the edge and the face of the scraper. By rolling the edge, a slight lip is made. When the scraper is drawn along the ski base this burr cuts into the base and peels off a very thin layer of base material
For burnishing thin scrapers, we use a special tool that has carbide pins to roll over the edge. Alternatively, the scraper can be placed vertically in a vise with the sharpened edge horizontal at the top. Sandwich the scraper between two pieces of thin wood so that the scraper can be clamped hard and securely held without being deformed. Take a large (10+ inch) chromed screwdriver in two hands (one at the handle, one at the tip) and push the shaft along the edge several times. The shaft should be almost horizontal at first and then increasingly more vertical to perhaps 30º from horizontal. Push down hard; the force will roll the edge over to make a lip. If the scraper is now re-filed a couple more times, just ever so lightly, the burr will be extremely sharp.
Do not over burnish the edge. All that is required is a slight lip. If the edge is rolled over too far, then the scraper has to be held too horizontally while scraping the ski and tends to chatter. An excessive burr can be removed by simply filing the edge.
STEEL SCRAPING (Return to top)
Clamp the ski onto the profile bench. Remove any wax from the surface of the base with a plastic scraper. Kick wax should be removed with a product specifically designed for ski bases ( e.g., Star's EcoSol).
Grasp the scraper with both hands and angle it rearwards; with the burred edge touching the base, the scraper will be tilted towards the tail of the ski at a slight angle (@30º from vertical). Skis are always scraped tip-to-tail. There are two methods of scraping: some skiers push, others pull. Both work equally well. Use the method with which you feel most comforable.
PULL METHOD: If the scraper is used with a pulling action, grasp the scraper with the thumbs on the rearward (tail) side about two thirds down the face. The thumbs will be about 2 inches apart. The first three fingers of each hand will be placed fairly flat along the ski tip side of the scraper, angled downward. The second fingers will be about 3/4 of an inch apart. The force for steel scraping using the pull method is aplied through the fingers. Outstretch the arms and pull the angled scraper along the ski base by bringing the hands towards the body.
Grasping the scraper in the manner described will support it, reducing the likelihood of bowing the scraper. If the fingers are held towards the ends of the scraper, it will bow under the force of the pulling. This will have the effect of removing base material from the edges of the ski. If the thumbs are moved to the edges of the scraper, this will cause it to have a concave curve and base material will be removed from the center of the ski base.
PUSH METHOD: When a pushing force is used, the thumbs are located on the tip side with the fingers on the tail side of the scraper. The thumbs are held closer together (about 3/4 inch apart) and the pushing force is with (through) the thumbs. The fingers are placed wider apart (about two inches between second fingers) and are used as backing for the force. Using the push method, the hands start near the body and push the scraper away, often with a little "body english" (push with the upper body).
Thicker scrapers bend less than thin scrapers. Many skiers prefer thick scrapers for this reason; they find it is easier to keep the scraper uncurved and therefore peel a base flat. However, if held as described, a thin scraper won't bow any more than a thick scraper. Furthermore, a thin scraper can be bowed on purpose in order to flatten the ski by removing material from either the edges or the center of the base.
Steel scraping skis has two basic functions: oxidized base material is removed at the same time the bases are made flat. The ski is down to non-oxidized "fresh" base material when nice thin peels come off the base. Oxidized material peeled from the base is fuzzy, often grayish (from a black base). If a ski has been stoneground, rilled, or has other structure (micro grooves along the length of the ski), the peels coming off the ski may not be wide but they will have a good longitudinal cohesiveness. That is, what is important is long strands being peeled from the base, not necessarily wide peels.
For optimum performance, the bases of skis need to be flat both side to side and down the length. Bases that are high at the edges ("railed") tend to be grabby when on edge. The skis behave unpredictably, especially when skating or in turns. When the center of the base is high ("base high"), the skis tend to be unstable and difficult to balance. The skis want to go every way but straight. Waves or ripples down the length of the ski cause pressure points on the snow, increasing friction and slowing the ski.
New skis come stoneground from the factory and are pretty flat down the length of the ski. Older skis often become base high. Ripples can develop along the base through the wax scraping process. Furthermore, skis that are perfectly flat when new will come out of true after several waxings. This is because the base material is not absolutely uniform and will absorb wax in differing amounts along the ski base. When a ski base absorbs wax into its pores, the base swells. Therefore, while skis should be made fairly flat when brand new, absolute flatness should not be sought until after the skis have been waxed and skied at least 10 times.
PEELING THE BASE (return to top)
The scraper should be in motion before touching the base. Gradually apply pressure until the scraper just starts to remove base material. Keep pushing or pulling in one steady even motion until the end of the stroke when the scraper is gradually lifted from the base. Do not start or stop abruptly. Feather into the scraping motion, scrape, then feather off the ski.
Many light passes are better than attempting to make a couple thick peels. Work a section of the ski (12-24 inches) at a time, starting at the tip. Overlap the sections being scraped and work down the ski. Really long peels are not important.
FLATNESS: Place the scraper across the width and sight down the base. A true bar (roll pin) can also be used and is essential on clear bases. Check the ski at several points along the entire base. It is quite possible for a ski to be base high in one area and railed at another. Bend the scraper if necessary to emphasize removal of material from either the center or the edges. Scrape a little, then recheck for flatness. Do not concentrate on one area - work along a significant portion of the length to ensure that the ski doesn't develop waves.
To remove ripples from a ski base, turn the scraper at a slight angle (side to side) but pull or push it straight down the ski. Be careful, the scraper will want to go sideways. Drop a finger down along each side of the ski to act as a guide.
When the base material being scraped off turns from fuzz to thin peels (even if short or narrow), then good fresh base material has been reached. If the bases are also flat, then the peeling process is complete.
DETUNE THE EDGES: Sharp edges are undesirable on cross country skis because they make the skis grabby. With skating skis, a sharp edge will cause the ski to hook into the snow during the push-off, slowing the ski. The front 12-14 inches and the rear 5-6 inches of the edges should be made quite round. To determine the exact length which should be detuned, place the bases of the skis together and compress the camber. The areas of the tips and tails which splay apart - which carry little of the skier's weight - should be thoroughly rounded at the edge. The edges along the main portion of the ski should be slightly rounded.
The edges can be rounded by either using a steel scraper to lightly peel off the sharp edge, or by using a sanding block with silicon carbide sanding paper (120-220 grit). Sanding is probably the easiest method. Use light back and forth (lengthwise) strokes, being careful not to scratch the base (by being too horizontal). Sandpaper raises "hairs" of base material, which can be removed by very lightly scraping with a sharp steel scraper.
STRUCTURE (return to top)
When a ski moves across snow, the snow crystals are melted at the point of contact and the ski glides on a thin film of water at each contact point. A water droplet can become attracted to both a snow crystal and the ski base. As the ski base moves, the water globule is stretched and the resulting tension slows the ski. Wax in the surface pores of the base can significantly lower this water tension. Equally important is the "structure" in the base. We can think of structure as texture on the base surface which aids in releasing the water globule's adherence to the base. The texture of the ski base causes the globule to be released, breaking the tension.
Water tension increases with the moisture content of the snow, which in turn increases with both temperature and humidity. In cold dry snow, there is little free moisture (liquid water) around the snow crystals and little snow is melted by the friction of the ski moving across the crystals. As such, dry slide friction is the major component slowing the ski, not water tension. Therefore in very cold and dry conditions, very little structure is needed. Brushing the bases with a brass brush (working tip to tail) may be all that is necessary.
Most snow conditions, however, require additional structure. This structure needs to be applied parallel with the length of the ski base. This is because the ski is always moving straight forward, in the direction it is pointing. Crosswise structure is only going to increase dry slide friction. (A skating ski may be moving at an angle to the groomed track, but the ski is moving straight in the direction it is pointing. Angled structure makes no sense).
The easiest way to apply longitudinal structure is with a rilling tool. "Rills" are long lines pressed or cut into the base parallel with the length. A rilling bar consists of a flat bar of brass with teeth on the edge only.
The bar should be angled rearward just like a steel scraper and pulled down the length of the ski in one pass, tip to tail. The goal is to press - not cut - even and straight grooves into the base. Rilling bars generally have two different width teeth, with fine grooves on one edge and medium grooves on the other. Use the fine structure for snow in the teens (ºF), the medium for the 20's, and both in the wet snows (32F and above).
An easier tool to use is the Toko Structurite Nordic. Toko has redesigned this popular tool to accomodate the Beta race skis from Atomic. This tool, which we use routinely at SIERRA NORDIC, rolls along the base and presses in rills that are periodically broken. It comes with two interchangeable structuring rollers (0.9 mm for most snow conditions and 1.5 mm for moist to wet snows). For very wet snow use both rollers.
Another good rilling tool is the Super Riller from Swix. However, this riller will not fit on the Atomic Beta skis. It self-centers by lapping over the sides of the ski. Simply start at the tip and press down hard in one long stroke from tip to tail. The tool requires a profile bench vise that doesn't grip the sides of the ski too close to the base, and it can only be used on racing width skis. The Super Riller comes with a medium (0.75 mm) bit good for most snow conditions. In the teens, a 0.5 mm bit can be exchanged into the tool, or simply press lightly with the 0.75 mm. For wet snows, put a 0.75 mm rill over the top of a 2 mm rill.
In general, most ski conditions call for medium width rills (0.75 - 1.00 mm). Rills that are pressed into the ski will come out after a few wax jobs, but this is an advantage. As the weather gets colder, simply continue to wax and don't re-rill. If the snow becomes moist or wet, add wider rills. Other than that, simply rill the skis after every 6 - 10 wax jobs.
DE-BURR THE BASE (return to top)
Structuring a ski can rough up the surface of the base, even if there are no visible hairs of base material. Start by going over the base with a brass brush. While adding very fine structure brass brushing also lines all the surface fibers parallel with the direction of travel. Brush in long overlapping strokes, tip to tail.
Next, go over the base with a Scotch Brite pad. Do not use the green or brown color kitchen scouring pads. They are too abrasive. The white sheets and pads are the softest and the only choice.
Work the pad back and forth with a vigorous motion and medium pressure. Spend at least 5 minutes per ski, perhaps as much as 15 - 20 if the bases appear hairy. End with lots of one-way strokes tip-to-tail. The ski base should be very shiny.
An excellent tool for de-burring the base is to use a rotary (roto) brush which attaches to a power drill. With only a couple of passes down the length of the ski, a roto brush can do a better job than 15 minutes of hand brushing. For de-burring the base, some roto brush attachments consist of a cylinder with a velcro surface onto which sheets of Scotch Brite are attached.
WAXING (return to top)
After the bases are peeled and structured, they must be immediately waxed to prevent oxidation. Brand new skis should be waxed with a pure paraffin wax, without any additives like silicon, graphite, or fluorocarbons. Testing of different waxes from all the wax companies has found the Uniblock yellow wax from STAR to give the best penetration. It even goes into problem ski bases that just don't seem to hold wax.
The Uniblock wax from STAR penetrates into the pores of the skis, coating the surfaces of the base fibers (crystalline polyethylene) and mixing with the noncrystalline (amorphous) polyethylene and graphite particles (in black bases) within the pores. Paraffin wax and polyethylene blend very well and the ski bases literally drink-up this soft wax as it drops into the pores and voids of the base. New skis need lots of wax, which should be reapplied as the wax disappears into the base.
Older skis may or may not need to be re-waxed with a soft paraffin wax. If they have been heavily steel scraped, then start as if they were brand new skis. Otherwise, go right to the wax of the day. If the skis are being waxed well ahead of when they will be skied, then wax with a medium temperature wax.
Wax skis for 3-5 minutes, always keeping the iron moving and never allowing any portion of the ski to become too hot. The iron should never smoke and the top sheet of the ski should never become hot. Some ski and wax manufacturers recommend that skis be waxed in one direction only (tip to tail) in a single slow pass. This is to ensure that the ski base isn't overheated by waxing repeatedly back and forth. Overheating a ski base can cause it to delaminate or have bubbles form under the base. A back and forth motion is OK so long as the iron continually moves along (progresses down) the length of the ski. Just don't keep reheating the same area of the ski. Once the wax is melted, move on. Soft paraffin waxes melt at a very low temperature and will stay molten for some time. Harder more plastic waxes will solidify immediately after the wax iron moves away.
After the initial waxing of new skis, remove the soft paraffin wax when it has solidified but is still warm, then apply a second coat. If the skis are going to be stored, leave this second coat on the base as a protective coating (against oxidation and dings). If the ski is going to be used right away, again scrape off the wax shortly after it has solidified. One to three coats of wax of the day should then be applied, allowing the ski to cool between each coat. The ski should never be allowed to become overly warm.
Real fanatics will apply several base coats on new skis over the course of a few days. It takes at least three wax jobs with the final glide wax to purge the base of the soft "initialling" wax. The wax of the day mixes with the soft paraffin, slowly replacing it within the pores of the ski. The process of skiing between wax jobs actually gives better results than just repeated waxings. It takes at least 15 waxings (with skiing in between) before skis begin to reach their full potential glide speed. The more the skis are waxed, the better they glide, turn, and perform.
Prior to skiing, all surface wax needs to be removed from the base. If the wax is soft, it should be removed after the skis have cooled to room temperature. if the wax is hard and chips off the base at room temperature, it should be removed while it is still warm. Scrape off the wax with a plastic scraper, never a steel one.
Use the same technique with a plastic scraper as with a metal one. Remove the wax from the center groove with a plastic "groove scraper". Next, brush the bases to remove all the wax from the structure, then finally polish the bases with a soft (white) Scotch Brite pad or a horsehair brush. Roto brushes again come in very handy. They do a much better and faster job of removing wax from the structure, while at the same time buffing the base to be very smooth and fast.
All recommended waxes, tools, and supplies may be ordered from our On-Line Shop. Contact us for details on shipping your skis to Sierra Nordic for pro base prep & wax.