Why does white marble turn yellow?
It depends on the marble. For example, the famous marbles from Carrara would have a geological age of 200 million years. The Makrana marble in Rajastan is supposedly 150 million years old, the Crema Marfil from Spain was formed, 75 million years, and the Egyptian limestones’ only’ 60 million years. Find & Download Free Graphic Resources for Marble Texture. 19,000+ Vectors, Stock Photos & PSD files. Free for commercial use High Quality Images.
It depends on the marble. For example, the famous marbles from Carrara would have a geological age of 200 million years. The Makrana marble in Rajastan is supposedly 150 million years old, the Crema Marfil from Spain was formed, 75 million years, and the Egyptian limestones’ only’ 60 million years.
Causes and cures (and why we recommend white or very light marble never be used in a shower)
Examine the marble for veins on its surface and then flip the tile over to see if there is a crack, or fissure in the same place on the back of the stone. Some stones, such as Crema Marfil, are very prone to fissures and may be likely to crack if the fissure is deep enough. If the crack is located in one area and it extends across only a single tile, the crack was likely caused by a sharp blow to the tile. Sometimes, you will see a chip taken out of the tile where the object hit. In kitchens, especially, where heavy objects such as cans, pots, and pans get dropped, ceramic tiles frequently break.
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Sitting in my office one morning I received a call from a very upset homebuilder. He told me he was building a two million-dollar home and had installed nearly 3500 square feet of a white statuary marble tile. Over the weekend one of the water pipes broke in a bathroom and completely flooded the home.
They managed to vacuum all the water and started to assess the damages. Beside warped wood, soaked drywall and an irate homeowner, the marble tile seemed fine except for some minor water spotting. After several weeks the replacement of warped wood and drywall was completed, but he noticed the white marble had turned yellow in many areas. At first he thought it might be some type of residue so they tried cleaning the marble with some bleach and water but the yellowing was still there.
Meanwhile, the homeowner was getting more and more irate and was threatening a lawsuit. It was at this point that he called me.
The problem of yellowed white marble is not uncommon. All over the United States I have encountered marble that has turned yellow, and even brown. Although flooding is a common cause there are several other reasons this color change will occur.
Improper Maintenance
As marble wears, the highly polished surface begins to become scratched and worn. The wearing of this polish causes the surface to become rough and become a magnet for dirt. If improper cleaners are used, this dirt begins to accumulate in the pores of the stone can will turn yellow. It is surprising how often I have seen this condition on marble. Upon investigation in these cases I have often found dirty mops being used. Mops used to clean the restrooms and/or kitchens were also used to clean the marble floors. Floors are mopped with strong cleaners or wax cleaner combinations or with no cleaners at all.
Cure: If you suspect yellowing due to improper maintenance the marble tile will have to be cleaned with an alkaline marble cleaner. I would suggest a heavy duty stone cleaner. Be sure the stone cleaner you buy needs to be alkaline and not an acid since acid cleaners will dull the polish. Apply the cleaner to the marble and scrub with a soft brush. Be sure to rinse the floor thoroughly. It may be necessary to repeat this procedure several times to remove all the imbedded dirt. If after cleaning the marble is dull I would suggest that you call us to professionally re-polish your floors then follow with an application of a good quality penetrating sealer (impregnator). If after several cleanings the yellowing is not removed then consider the next cause.
Wax Build-up or Coating
Many marble floors are coated with waxes, acrylics, urethane and other coatings. Most of these coatings are not specifically designed for use on marble floors. Some of these coatings are of poor quality and the coatings themselves will begin to yellow. It is not uncommon for coating to be applied in multiple coats. As the coating builds up it becomes soft and dirt is easily embedded in the soft layer. These coatings require frequent stripping which is often neglected.
Another possibility along these same lines is that process sometimes used for polishing marble floors is known as re-crystallazation. If this process is applied to a white marble floor that contains moisture it will turn the marble yellow.
Cure: To remove yellowing due to a wax or coating buildup the marble will need to stripped with a commercial wax stripper. I would strongly suggest having this done by a professional. These strippers often require the use of abrasive pads which can scratch and damage the marble surface. If you do try it yourself, before undertaking the entire project perform a small test to determine results.
If the marble tile has been recrystallized, it will be necessary to remove the recrystallized layer. This layer can often be removed by a professional polishing the tile with a powder marble polish containing oxalic acid. If this technique fails then the tile will have to be re-honed. It is strongly suggested that the polishing and honing procedure be performed by trained individuals. If these techniques fail to remove the yellowing then proceed to the next possible cause.
Iron Staining
Many white marble tiles contain naturally occurring deposits of iron. Iron is a mineral found in stone and can occur randomly throughout the stone. If iron is present in the marble tile, it will begin to oxidize when exposed to water or other oxidizers such as acids and household bleach.
It is for this reason that we recommend not using white marble in a shower.
White marble tiles can remain for years without yellowing then over time may slowly turn yellow, and in severe causes, may turn completely brown. This oxidation process is accelerated when the tile is saturated as in the flood in the above example. This process of oxidation is similar to the rusting of metal. If you expose a brand new nail to water and air it will turn brown and rust. The same process is occurring with the iron in the marble. If water and/ or air is eliminated the iron will not oxidize. This is the reason certain white marble suddenly turn yellow.
The process is difficult to reverse and replacement of the tile may be necessary. The following stain removal technique has proved successful in several cases. Before testing this procedure it is important to first determine if iron is the cause.
Testing for Iron:
- Before assuming the marble is yellowed due to iron, be sure to attempt cleaning and stripping as outlined in the first two possible causes above. If these procedures fail then testing for iron will be necessary.
- If a flood has occurred or excessive water was used first check the water for iron. If any amount of iron is detected then it is possible iron has entered the stone through the water supply. To eliminate the iron there are chelating chemicals that can be added to the water to prevent the iron from staining. This is very important if the tile is cleaned with this water.
- Even if the water contains no iron the tile can be checked for iron content. We can remove one tile and have it analyzed total iron. If there are spare tiles that have never been installed it would be a good idea to also have them tested for total iron. If iron is present naturally in this stone, it will probably be detected in the spare tiles. If the results return with iron present then the following procedure should be tested.
- We can check the tile for moisture using a moisture meter. If the tile contains water, it is very possible that iron is beginning to oxidize.
The Process for Removing Iron Staining:
- Prepare a solution of water and the following chemical: Sodium Hydro sulfite and Sodium Metabisulfite. These chemicals are available in a product called Iron-Out® you may have seen at your plumbing supply or home center.
- We will mix a solution in water and apply to the effected tile, and allow the solution to soak into tile and kept wet for several hours. It is important that the solution not be allowed to dry. After several hours pick up excess solution with a wet vacuum and rinse thoroughly with water and a chelating agent such as EDTA.
- Be prepared to expect that the marble may need to be repolished since these chemicals can etch marble.
If the above procedure fails we can then prepare a poultice with diatomaceous earth and the Iron Out™. The poultice mixture will be applied to a small area and covered with plastic wrap. After 24 hours remove the poultice paste and rinse the area with water and a chelating agent. If the stain is removed, the entire floor can be treated. If the stain still remains then replacement is the only solution.
Feeding the monster for mac. NOTE: There are also some new chemicals that are available which contain Ammonium Thioglycolate which look promising for removing iron oxidation.
The yellowing of white marble is a common problem. New installations should be sealed with a good quality penetrating sealer (impregnator) which will help prevent oxidation of the iron by eliminating moisture.
Image courtesy: flickr.com
Marbles have been around since early times. Various civilizations used them for recreation, like they are used in modern times. The Egyptians believed that those that were made with animal bones could serve as spiritual mediums.
Although not as many people play marble games as before, they are still popular in different parts of the world. Aside from being used for playing, they are also made into a collection, especially the vintage pieces, which are pricier than their modern counterparts.
Mass production of marbles started only in 1800’s. Vintage marbles are only limited in number, which is why they are more expensive. If you want to start making them part of your collection, you should know how to identify vintage marbles.
Watch this video, summarizing a book on collecting antique marbles and identifying them by Paul Baumann:
This could help you determine if the item is authentic in order to get your money’s worth. Here are some ways to determine if a marble is vintage or not:
1. Look for the Pontil
Most vintage marbles were made by hand through the process called glassblowing. During this procedure, a stick is used where the marble is attached.
Once done, the stick is broken on its end. This leaves a tiny rough patch on the marble, which is known as the pontil.
Although most new marbles are made by machine therefore leaving them without pontil, there are still those that are handmade.
That being said, the pontil is just one of the factors to consider when determining if the marble is vintage or not. Other factors must still be considered in order to arrive with the right conclusion.
2. Check Their Appearance
Vintage marbles are typically more attractive and brighter than modern ones because they were individually made, compared to the new ones that were made in high quantities.
This may be a little challenging for new collectors, but experienced collectors would be able to tell the difference. If you know one, you may want to get their help.
Moreover, you may check on books that specialize on antique marbles. There are specific marble patterns that were made during a certain period or from specific countries. Familiarizing yourself with these could help.
Other ways to improve your knowledge in this area is by attending marble collector events. Pride of the Prairie Show and Orange County Marble Show are some of these.
You may also join marble collector organizations in order to connect and learn with people of the same interest who could impart their knowledge and experience to you.
Here’s a video that shows a collection of vintage marbles. See if your marble looks like any of them:
3. See the Flaws
Vintage marbles are usually not perfectly made. Since they were made by hand, it was difficult for glassblowers to come up with a perfect one.
'Vintage marbles are only limited in number, which is why they are more expensive.'
This may not be the case with modern marbles. They are done precisely and flawlessly because they are made by machines that were designed for this task. Aside from the pontil, antique marbles typically have flaws including bubbles.
This doesn’t mean that you need to look for a damaged or broken marble, as this would affect its value. However, do not expect to see a perfect looking marble, because if you get one, it may probably not be vintage.
4. Determine the Quality of the Glass
The quality of glass used when making marbles in the old days was high. This is because they were used for playing so they shouldn’t easily break.
While modern marbles are also used for playing, the glass used is not as high quality as the old ones so they could easily break. They are cheaper and produced in mass volumes so they can be replaced easily even when chipped or damaged.
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5. Consider the Seller
If the person selling the marbles is old, they are more likely to be old too. However, this is not always the case as it could also be possible that the marbles were purchased recently or someone might have just given them to him.
Make sure to ask the seller about the origin of the marbles. If in doubt, go back to the different factors discussed on how to identify an antique marble.
Even if you have determined that the marble that’s being offered to you is vintage, it doesn’t mean that you should get it at a high price. Consider the condition too. If it’s too worn out, it may not be as valuable as it would have been if it’s in good condition.
References:
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