After a bit of informal research on my own, I've concluded there are a few things or conditions that can cause the pasta machine to discolor polymer clay. This information may differ a little from what you've been told up til now.

From personal research and testing, I've concluded that there are three discoloration types:
1) light or dark grease or oil along the outer edges of the clay sheet,
2) tiny (hard or soft) bits of various colored clay deposited on various areas of the clay sheet,
3) dark to black smears or streaks on various areas of the clay sheet.

1) greasy, oily smears along the edge of the clay sheet.
Lubricants are used to keep a pasta machine's metal parts turning as smoothly as possible. Because the pasta machine is intended for food use, it unlikely the manufacturer would improperly lubricate or over lubricate it. It would be a real turn off to see one's pasta full of gear grease. However, for whatever reason, if there is too much lubrication, it can migrate onto the roller surfaces and scrapers, then to your clay.

This is the easiest discoloration problem to correct. Hold a paper towel on the edge of the rollers while cranking the pasta machine to absorb the excess lubricant. Then pass light colored scrap clay through the pasta machine to see if the problem is gone.

2) Bits of various colored clay on various areas of the clay sheet.
Sometimes the bits are soft, sometimes they're hard. What they are are little return gifts that the scrapers had scraped off clay sheets as they passed by, clay that accumulates between the rollers and the scrapers over time. That's why those little bits can be of various colors. Under certain circumstances, the old clay decides to escape from the scrapers and hitchbacks onto the nice new clay.

To correct this problem: remove the scrapers and wipe away all that residue clay with a clean paper towel. If the clay is hard or real difficult to remove apply a little WD-40 or mineral oil and let it soak into the clay to soften it.

3) Black rust: those black smears or streaks on various areas of the clay sheet.
This is the biggest complaint of all. Most assumed that these streaks are caused by the pasta machine's lubricant. Most complain about being plagued by some streaking throughout the course of using their pasta machine, no matter how old it is. Other's don't notice it. Most say it's more noticeable when their machine is new.

After a bit of research, I learned the rollers and scrapers of apparently all pasta machines are made of steel, probably carbon steel, which can be very reactive to various chemicals, oxidizers, acids and alkalis. Many fine cooking knives are made of from carbon steel. So, steel is not invincible, not inert.

With steel there are two common reactions or oxidations - red rust (FeO2) or black rust (FeO3). Apparently, some plasticizers in clay are oxidizers, promoting black rust; that infamous dark to black streaking.

I noticed because the clay that seems to promote oxidation the best is plain ole soft translucent. This makes sense because it has the highest ratio of plasticizer per weight/volume. But any polymer clay leaves residue on the rollers and scraper blades which can react with the steel.

You're probably just thinking, "Stop! I just want to know how to get rid of those pesky streaks?"

Like fine cutlery for the kitchen, pasta machines require a bit of care and consideration, probably a bit more than you thought; definitely more than I thought. In general, if you're having black rust problems (*if* because not everyone does), you'll need to remember to clean away as much of the plasticizer and clay as you can. It's like remembering to not let your expensive steel carbon knives sit in water for too long.

Recently [27sep09] , I tried many different chemicals on the rollers of an unused Atlas pasta machine, dated 1999. (Yes, I avoided using the thing for 10 years because it oxidized and soiled my clay so badly). All of the substances listed below caused instant or near instant black rust on this machine (some created a lot more black rust than others):

• any metal polish, Brasso
• isopropyl alcohol (99%)
• nail polish remover
• coconut oil
• WD-40
• Formula 409
• Greased Lightning
• carburetor cleaner
• heavy duty silicon spray
• and probably a few other household cleaners I forgot that I tried

The point is new roller steel can be extremely reactive! So far, I've found one humble substance that actually removed the black rust caused by all those chemicals listed above.

Ammonia!

Yup, that smelly, 'hold your nose' ammonia. I figured if acids are infamous for promoting black rust on carbon steel, maybe a mild alkaline substance would counteract it. I just happened to have a bottle of liquid sudsy lemon-scented ammonia under the sink that's been itching for something to do.

So here's what I have done, a few times now, to remove the black rust:

1. Removed the scraper blades (they need to be out of the way since they will trap liquids)
2. Put the machine back together (without inserting the blades)
3. In a small bowl, added about 1/4 cup of clean water and 1-2 tablespoons of the liquid ammonia (precise measurements are not necessary)
4. Dampened a clean paper towel with the ammonia solution, squeezed out excess liquid
5. Laid the towel across both rollers, pressed firmly and rotated the rollers several times
6. Checked the towel for black rust residue, if present, repeated with another clean, damp paper towel
7. Once the paper towel looked clean, thoroughly dried the rollers with a dry paper towel
8. Cleaned and dried the scraper blades the same way
9. After the rollers and blades are thoroughly dry, re-inserted the blades.

I can only presume that over years time, the steel's reactiveness lessens. My well aged, well used Atlases don't seem quite so reactive. So I think the above steps are more useful to those who have just acquired a new pasta machine with uncoated (no Teflon) rollers.

For those who have fairly minor black rust problems, I would recommend just wiping down the rollers, etc. with a dry paper towel when you're done using your PM for the day, especially if your machine is new. Just as you shouldn't leave fine steel cutlery soaking in water, don't let raw clay or residual plasticizer linger on the roller or scaper blade surfaces. And before rolling light color clays, check for black rust with a clean paper towel. If present, you can do the ammonia cleaning step above to remove it.

Given the potential reactiveness of the steel rollers and scraper blades, I'm also very careful about substances used to clean them. I definitely don't use anything that is considered a moisturizer, anything that contains glycerine or any other emulsifier. Moisturizers and glycerine can be thought of as thick water. They coat like a grease or cream and contain lots of water. While it is great for moisturizing skin, they linger on the metal and can cause steel and iron to oxidize.

* Since I originally posted this tute (probably in 2002 or so), pasta machine models have changed. I can't say it's been an improvement, though. More plastic has replaced metal, some scraper blades have plastic covers, some PMs don't even disassemble, frames are flimsier! My recommendation is if you decide to take apart your PM, do so carefully. Document every possible state, so you can reassemble it correctly.

On the crank (handle) side of the pasta machine, use the small point Phillips head screwdriver to remove the small screw that holds the outside half of the side panel. Remove the outside half of the side panel.

Flip the pasta machine so you can access the bottom. Use the medium point Phillips on the two screws of one foot to remove the crank-side foot.

Flip your machine so it's upright again. Use the 10mm socket wrench to remove the two nuts that attach the inside half side panel. Be careful, the inside panel may have sharp edges. Grip the panel then wiggle, rock, cajole it to pull it off.

The panel held several things in place; the pair of smooth rollers, a pair of scrapers, a pair of bracing rods, and a pair of fenders.

Toss those fenders aside. They're history! You'll never need them again.

Get ready to pull out one of the scrapers. Before doing that however, carefully note their position and their insertion points into the other side panel. This observation is very important!

Now, pull just one scraper completely out and examine the edge. You may notice a buildup of clay. Use a paper towel lightly soaked with your choice of cleaner, degreaser or lubricant to soften and wipe all the clay away. Then wipe the scraper clean with a clean, dry paper towel. Put that scraper back in its slot.

Pull out the other scraper and clean it the same way as the first scraper. Return the second scraper to its respective slot. The major cleaning task is done! If necessary and you have some silicon grease you can take this opportunity to lightly grease the ends of the rollers. Take care to not over grease, otherwise the excess can end up on your clay.

Note: Positioning the scraper blades is very important to a successful outcome of using pasta machine. Without them, the clay would stay on the rollers and keep rolling around, building up layer after layer.

Once the rollers have done their work, the scraper blades guide the clay away from the rollers. The scraper blade edges needs to remain smooth and close to the rollers.

If you jam tools into the space to remove scraped clay, or if you add bits of metal or sand, etc, in the clay and pass it through the pasta machine or if you force clay pieces between the rollers that are too thick, you could damage the scraper blade edges or even bend the blades, making them annoyingly ineffective. You'd need to replace them

Now let's put it back together.

Position the inside side panel so that its position matches its counterpart on the other side of the pasta machine. Align it so that the rollers begin to slide into their openings. Next, align the bracing rods so they can begin to slip into their openings. Finally, align the scrapers so their tabs are directly in front of their slot openings in the inside side panel. Press the panel until it kinda clicks into place. Replace the nuts on the bracing rods.

Flip the entire machine so the bottom is up. Replace the foot, screw in those two little screws.

Flip the machine so it is upright once again. Replace the outside side panel and put its screw back in.

Slip a clean dry paper towel down between the rollers and with the handle inserted, turn the rollers but don't let the paper towel pass through. Crank clockwise and counter clockwise. Finally, pass a piece of light colored scrap clay through the rollers a few times. Check the clay to make sure it's clean. You're done. When you've got the right tools and you've done this once or twice, this entire procedure takes about 5-10 minutes!