Oxidation / Corrosion vs. Wear in Antique Rugs
Corrosion, oxidation and wear are terms that you might hear when buying an antique rug. These are both a type of change that occur in rugs over time, but they are very different. The presence of corrosion / oxidation gives the rug an aged look and patina which lets you know that it is an authentic antique. Let’s explore how oxidation / corrosion and wear happen so that you will understand them as you evaluate rugs for your collection.
Oxidation, Corrosion and Metals in the Dyeing Process
Corrosion and oxidation are pretty synonymous terms that you typically associate with metal, not rugs. When metal corrodes / oxidizes, it reacts with oxygen in the air. If the metal is iron, then it will result in rust. When copper corrodes / oxidizes it turns green, like statue of liberty in NYC, and breaks down with time. These are all signs of the passage of time and indications that an item is old.
What people sometimes don’t realize is that when we talk about oxidation or corrosion in rugs, we are still talking metal. Some natural carpet dyes have metals in them and are comprised of materials such as iron, copper, chromium, tin and aluminum to allow the color to adhere to the fiber. Metals and metallic salts make the dyestuff more permanent and lightfast. This means that it will not fade over time, and the colors will, for the most part, stay truer. This is what allows many rugs, carpets and textiles to remain nearly as bright and vibrant as when they were created, even after several hundred years of use.
If the rug is an antique, iron and copper were used, as they were the most common metals used in the color dyeing process. Iron is usually in the form of ferrous sulfate. Copper is usually soaked in vinegar to extract cupric acetate that is then used to dye the cloth. Chemically, these metals act as a bridge between the fiber and the color molecule, allowing it to create a tighter bond.
How Oxidation and Corrosion Changes Rugs
The dye colors created with metallic salts are responsible for the beautifully harmonious tones that we associate with natural dyes, but they have a “dark side”. Over time, these metals that are within the dyes themselves will begin to oxidize and corrode. When they do, it can break down the wool or silk fibers with them. As this occurs, the rug pile will become brittle and flake off a tiny little bit at a time. When you run your hand over these oxidized areas, the corroded sections will feel a bit rougher and have a lower pile height than the areas around it that didn’t use metals in the dye. This creates a high / low embossed look and feel and will be especially present in the darker colored areas of the design.
Corrosion might occur over the whole rug, but it is seldom evenly worn as different dyes have different concentrations of the metallic elements. That is why you might find that the lower pile corroded areas are only noticeable in certain colors. It is more common in darker colors like brown and black, because those colors require more iron to create. This uneven pile is what gives the carpet that high-low appearance. You will sometimes see white warp and weft threads of the rug’s foundation peaking through in areas of low pile.
Recognizing Actual Wear – Not Corrosion
Wear in rugs can look similar to corrosion in some ways. That said, there are a few things that distinguish it from oxidation. A rug wears simply as a result of people walking on it over time. Wear reflects the utilitarian purpose of the rug.
As people walk on the rug over long periods of time, little pieces of the wool break off. Eventually, just as with corrosion, the white warp will begin to show through. This might appear as little white flecks, singular white knots, or it might be more pronounced, and you can see white warp threads on the front (pile side) of the rug. On many rugs with heavy wear on the pile, the fringe or the ends will tend to be ragged or very short, too.
Differences Between Corrosion and Wear
Corrosion will usually differ according to different color areas. Wear is more uniform across the surface where people were walking and will not show more or less wear based on color. Sometimes, a carpet might wear all over, but it might also occur where the rug was walked on the most. For instance, there might be a visible area down or across a section of the rug where you can see evidence of foot traffic.
Now that you understand the difference between corrosion and wear, you will be able to recognize it in antique rugs. Corrosion and wear are not always a bad thing in antique rugs. They give rugs a unique shabby chic texture and character and let you know that it is an authentic antique.
Feel free to take a look around at the fine antiques in our collection and see if you can spot the hallmarks of a real antique rug through corrosion and wear.