About Stone Stains

We all know what a stain is, right? . Or do we .

Let’s start by saying that a stain is a discoloration. So far, so good.

The fact is, however, that not all discolorations are stains. Let’s take, for example, a piece of fabric. Fabric is typically absorbent; therefore if we spill some liquid onto it, the material will absorb it. If it’s only water, we’ll have a temporary stain. In fact, once it dries the fabric will go back to its original color (plus, maybe, some mineral deposit can we can just brush away), but if we spill some coffee, or cooking oil on it we will make a stain, because the fabric will absorb the staining agent and change its color in a permanent way, unless we do something to remove the agent from the fabric.

On the other hand, if we spill some bleach on the same fabric, we will still have a discoloration, but it can hardly be defined as a stain, because it’s actually a permanent damage to the die that originally made the color of the fabric.

When it comes to natural stone we are, once again, dealing with stains and “stains.”

All stones are, more or less, absorbent. One may say that diamonds, or any other gemstones are not absorbent. That’s right, but a gemstone is not actually a stone: it’s in fact made of one crystal of one single mineral. All other (less noble) stones are the composition of many crystals, either of the same mineral, or of different minerals bonded together. The “space” in between these molecules of minerals is mostly what determines the porosity of a stone. That said, what’s next is the fact that the porosity of stones varies greatly, and so does, of course, their absorbency. Some of them are extremely dense; therefore their porosity is minimal. What this translates into is the fact that the absorbency of such types of stone is so marginal that – by all practical intents and purposes – can be considered irrelevant. Some other stones present a medium porosity, and some other ones – at the very end of the spectrum – are extremely porous. Because of their inherent porosity, many a stone will absorb liquids, and if such liquids are staining agents, a true stain will occur. Consequently .

A true stain is a discoloration of the stone produced by a staining agent that was actually absorbed by the stone.

A “stain” is something else that has nothing to do with the porosity (absorbency) of the stone: It has instead to do with its natural chemical makeup. It is still a discoloration, but – like with the example of the fabric and the bleach above – it’s actual damage to the stone surface. All those “stains” that look like “water spots”, or “water rings,” are actually marks of corrosion (etches) created by some chemically active liquid (mostly – but not necessarily limited to – acids) which had a chance to come in contact with a stone that turned out to be sensitive to harsh chemicals. All Calcite-based stones such as marble , limestone, onyx, travertine, etc. are sensitive to acids; therefore they will etch readily (within a few seconds). Many a slate, too, will etch, and so will a few “granites” that, instead of being a 100% silicate rock, are mixed with a certain percentage of calcite.

Now let’s see what to do to remove stains and “stains.”

How to Remove a Stain – Poulticing Method.

Definition of a Poultice.

What’s a poultice? It is the combination of a very absorbent medium (it must be more absorbent than the stone) mixed with a chemical, which is to be selected in accordance with the type of stain to be removed. The concept is to re-absorb the stain out of the stone. The chemical will attack the stain inside the stone, and the absorbent agent will pull them both out together.

It’s intuitive that while the absorbent agent can be the same all the time, regardless of the nature of the stain to be removed, the chemical will be different, in accordance with the nature of the staining agent, since it will have to interact with it.

The absorbent part of a poultice could be (in order of the writer’s preference), talc powder (Baby powder), paper-towel (“Bounty” or “Viva” are the best), and diatomaceous earth (the white stuff inside your swimming pool filter) for larger projects.

Consumers can also find so-called “professional poulticing kits” at a local tile and marble retailer. It is the opinion of this writer that they are nothing but a marketing gimmick. In fact, no true professional ever uses any of them! Not only are they expensive, but more importantly, they are limited to removing only the type of stains the kit’s chemical agent is designed for. Everybody – with no experience whatsoever – can make their own homemade poultice, which will be just as good as the “professional kits” (if not better!) Moreover, the consumer will purchase the (easy-to-find) chemicals that will be deemed right for the task at end.

As we said before, the chemical must be selected in accordance with the nature of the staining agent. There are five major classifications of stains:

  1. Organic stains (i.e. coffee, tea, coloring agents of dark sodas and other drinks, gravy, mustard, etc.)
  2. Inorganic stains (i.e. ink, color dies, dirt – water spilling over from flower and plant pot, etc.)
  3. Oily stains (i.e. any type of vegetable oil, certain mineral oils – motor oil, butter, margarine, melted animal fat, etc.)
  4. Biological stains (i.e. mildew, mold, etc.)
  5. Metal stains (i.e. rust, copper, etc.)

The chemical of choice for both Organic and Inorganic stains is Hydrogen Peroxide (30/40 volumes – available at your local beauty salon. The one from the drugstore is too weak, at 3.5 volumes). Sometime, in the case of ink, Denatured Alcohol (rubbing alcohol) may turn out to be more effective.

For Oily stains our favorite is Acetone, which is available at any hardware or paint store. (Forget your nail polish remover: some of them contain other chemicals, and some other ones contain no acetone whatever.)

For Biological stains, one can try using regular household bleach.

For Metal stains, our favorite is a white powder (to be melted in water), which is available at fine hardware stores all over the country under the trade name of “Iron-out.”

How to Prepare a Poultice and Use It to Remove Stains.

Now that we have all our ingredients, we can prepare the right concoction to remove the stain at hand.

WEAR RUBBER GLOVES ALL THE TIME, WHILE USING CHEMICALS!

If you’ve chosen talc powder (baby powder) as your absorbent medium,

1.     You mix it – using a metal spatula or spoon – in a glass or stainless steel bowl, together with the chemical, to form a paste just a tad thinner than peanut butter (thin enough, but not running.) Now you have made your poultice.

If you’re attempting to remove a metal (rust) stain, first you you melt the “Iron-out” with water – according with the directions written on the container – and then you mix it with an equal amount of talc powder, adding water if it turns out to be too thick, or talc if it’s too “runny”.

2.     Apply the poultice onto the stain, going approximately ½” over it all around, keeping it as thick as possible (at least ¼”.)

3.     Cover the poultice with plastic wrap, and tape it down using masking tape.

4.     Leave the whole thing alone for at least 24 hours, and then remove the plastic wrap.

5.     Allow the poultice to dry thoroughly! It may take from a couple of hours to a couple of days or better, depending on the chemical. Do NOT peek! This is the phase during which the absorbing agent is re-absorbing the chemical that was forced into the stone, together (hopefully!) with the staining agent, and you do NOT want to interrupt that process!

6.     Once the poultice is completely dry, scrape it off the surface of the stone with a plastic spatula, clean the area with a little squirt of distilled water, then wipe it dry with a clean rag or a sheet of paper-towel.

If the stain is gone, your mission is over! If some of it is still there, repeat the whole procedure (especially in the case of oily stains, it may take up to 4 or 5 attempts!). If it didn’t move at all, either you made a mistake while evaluating the nature of the stain (and consequently used the wrong chemical), or the stain is too old and will not come out, or it was not a stain, but it was a “stain” instead.

If you decide to use paper-towel instead of talc powder, make a “pillow” with it (8 or 10 fold thick) a little wider than the stain, soak it with the chemical to a point that’s wet through but not dripping, apply it on the stain and tap it with your gloved fingertips to insure full contact with the surface of the stone. Then you take it from the point 3 above.

How to Remove a “Stain”.

We already established what a “stain” is. It’s obvious that if you keep thinking “stain” just because those “weird things” look like stains (water spots, or rings), you’re misleading your thoughts, because you would automatically research in the database that you have in between your ears, for a solution pertinent to stain removal, that, of course, would turn out to be totally useless. Now the question is: “How do I remove a chemical etch-mark, which, as seen, is not a stain but a surface damage?”

You don’t!

In fact an etch mark can be effectively compared to, and defined as, a shallow chemical scratch. A scratch is something missing (a groove), and nobody can remove something missing. It would be like trying to remove a hole from a doughnut! The only thing one can do is to eat the doughnut, and . the hole is gone! Same thing with a scratch: One must actually remove whatever is around the groove, down to the depth of the deepest point of the scratch.

We’re actually facing a full-fledged – though small in size – stone restoration project!

Can you, average Mr. or Mrs. Homeowner handle the task?

The answer is: Maybe.

If it is polished marble or travertine or Onyx, then there’s hope. If it is hone-finished marble or travertine, terrazzo, or hone-finished slate (like a chalk-board), or mixed “granite”, then you’d be better off hiring us. If it’s a cleft-finished slate (rippled on its surface), than nobody can actually do anything about it, other than attempting to apply a good quality stone color enhancer.

Concentrating now on the case of polished marble or limestone or travertine or onyx or terrazzo, if the etch is severe (deep to the point that it looks and feels rough), then you do need a professional stone refinisher. But if the etch is light (the depth is undetectable by the naked eye, and it looks and feels smooth), then there are a few polishing creams or powders, available to the do-it-yourselfer that are user-friendly enough to be handled by just about everybody. Just follow the directions on the container.

Finally, we may have a combination of a stain with a “stain”. For example, if some red wine is spilled on an absorbent polished limestone, then the acidity of the wine (Acetic acid) will etch (acid burn) the surface on contact, while the dark color of the wine will stain the stone by being absorbed by it. In such a case, first you remove the stain by poulticing (Hydrogen Peroxide), then you repair the “stain” by refinishing the surface. In most instances you can remove the stain yourself but the floor will most often be left with some degree of etching, which will require restoration. If this is the case please feel free to give us a call and we would be glad to help, no job is too big or too small. We understand that your polished floors are the focal point of your home and we want to help you make them look there best! Contact us today if you have any further questions.

For more information on terrazzo restoration please visit our new terrazzo site www.terrazzoguy.com