Now we will explore the nature of PVC, and its ingredients so that we may understand how they contribute to problems we may encounter in our preservation efforts.

One of the most important things to understand about PVC is the relationship between PVC resin and plasticizer, and the concept of plasticizer migration. When they are mixed, the liquid plasticizer coats the powdered resin particles, and when heat is applied the PVC resin absorbs the plasticizer which in turn swells the resin particles, promoting their "fusion." I put fusion in quotes because, unlike other plastics, the mixture of resin and plasticizer are not actually chemically bound or fused together; they are a physical mixture, just as a combination of salt and pepper would be called a physical mixture - with magnification and perseverance, you can separate the salt from the pepper.

As such, plasticizer moves freely within PVC because it remains fluid, even after heat has been applied. This movement of plasticizer is called "plasticizer migration." This phenomenon is responsible for the spreading of stains - whatever the origin - seen in Smurfs. An example many collectors are familiar with is ball-point pen ink marks that have soaked into the PVC. Such stains often have indistinct edges – they “bleed” into the adjacent area. This is because the stain spread as the ink was carried through the PVC by migrating plasticizer. Stains not only spread on the surface of PVC, but they spread down into the PVC, which is why stained Smurfs can be so hard to clean. Many times, however, they *can* be cleaned, and we will explain how you can do that later in this article!

While some plasticizer migration is normal in PVC, poor PVC formulations can result in excessive migration of plasticizer to the surface of PVC (also known as "blooming") giving it a slick, greasy feel. If it is not cleaned, this plasticizer can oxidize, resulting in yellowing. Oxidized plasticizer can also look like dirt, or it can be orange or gray and it can also form a crusty surface. We will also explain how to correct this problem later in this article!

Body oils will also be absorbed by PVC, and drawn into the PVC through plasticizer migration. These body oils also turn yellow when they oxidize. We will discuss later how to correct this problem and what you can do to prevent it from recurring!

Both plasticizer and body oils can also serve as nutrients for microorganisms that can grow on PVC. Bacterial growth leads to a moldy odor, fungus can stain and grow roots into the host substrate (also known as your Smurf!) and a type or microorganism called an actinomycetes can grow in PVC, producing a pink or red stain that spreads as the plasticizer migrates. We will teach you how you can remove all staining, fungal roots, and odor from Smurfs that have already been attacked, and also tell you how to prevent it from recurring later in this article!

Just as plasticizer can migrate and bloom on the surface of PVC, so can lubricant, if too much was added to the formulation. This can appear as a white hazy film. We will tell you how to remove this haze from PVC later in this article!

Various types of staining can result when PVC or its components react with foreign materials that may come in contact with them. Newsprint or dyes can transfer to the PVC. Sulfur (possible sources are Tarn-X, pollution, and cooking fumes from foods preserved with sulfur dioxide, such as dried fruit) will react with the Chlorine in PVC to form sulfur chloride, which manifests itself as brown staining. Copper and brass will stain PVC green.

Some staining can occur when ingredients in PVC react with each other over time. This is called cross-staining. A lead or cadmium heat stabilizer can react with a sulfur containing filler or colorant causing a gray (lead sulphide) or yellow (cadmium sulphide) stain. Other cross staining that can occur in various PVC formulations can be yellow-orange, red, or black. Whatever the source of the stain, over time migrating plasticizer will bring it to the surface and/or deeper into the PVC. Fortunately, nearly all stains can be permanently and safely removed from Smurfs, and we will explain how to do that, and how to avoid stains in the first place, later in this article!

One stain that cannot be removed is brown streaking caused by exposure to high temperatures. PVC deteriorates when exposed to heat by giving off the acidic compound hydrogen chloride. When this happens, the PVC loses chlorine, and the manifestation of this loss is brown streaking. PVC degrades swiftly at temperatures of 200º F. However, degradation will occur at lower temperatures over a long enough period of time, even though the temperature does not reach 200º F. It is not possible to reverse this kind of staining, so it is very important that you always store Smurfs in a cool environment.

Yet another important thing to understand about PVC and heat is that it is a "thermoplastic plastic." This means that it can be reheated and molded into another shape (as opposed to "thermoset plastic," that cannot be molded into another shape).

It may be useful to think of a thermoset plastic as being like egg yolk, and thermoplastic plastic as being like butter. Once you cook egg yolk, you cannot soften it by reheating and form it into a new shape. However, butter may be molded into a shape, softened and remolded again and again.

Although temperatures of up to 450º F may be required to fuse PVC resin during production, much lower temperatures can cause finished PVC to distort. Because PVC is a thermoplastic plastic, figurines that are exposed to high temperatures (in an attic or garage for example) while the pressure of being crammed into storage distorts their normal configurations, will remain warped after temperatures have cooled off. Some figurines may not stand correctly; others will have thin parts bent at the wrong angle. In effect, they have been reheated and molded into a new shape. Fortunately, this can be fixed, and we will tell you how later in this article!