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Remove Stains From Natural Stone Using a Poultice

Natural stone can be discolored by one of many types of substances. Everything from biological stains such as algae, moss, and mildew to organic stains like coffee, fruit, leaves, and tree bark. Depending on the type of stain being treated and the kind of stone the stain is on, specific techniques should be used. In this article we are going to discuss how to remove stains from natural stone using a poultice powder. We will not only talk about using a poultice on stone stains, but we will also mention some specifics regarding the technique as well.

What is a Poultice?

A poultice is defined by the Natural Stone Institute as "a liquid cleaner or chemical mixed with a white absorbent material to form a thick, stain removing paste". Furthermore, some kinds of stains must be removed using a poultice. For example, inorganic metal stains on stone surfaces require this method of stain removal. Stone poultices are not the only kind of poultices used. For example, there are poultices use for drawing out infections from the human body. So, the method is not odd or strange, by any means. It is simply a controlled way to make the stain leave the stone the same way it entered it.

Are All Poultices the Same

There are various materials suitable for using as a poultice. The idea is that the poultice be absorbent. Poultices can be made from any of the following materials:

  • Diatomaceous Earth
  • White Paper Towels
  • Fuller's Earth
  • White Cotton Balls
  • Kaolin
  • Gauze Pads
  • Whiting
  • Powdered Chalk
  • Talc
  • White Molding Plaster

There are some important things to know about what materials you use with which chemicals to make your paste. For example, using an acidic chemical with whiting or iron-type clay like fuller's earth will stop the effect of the poultice. Many people find that purchasing a premixed poultice that only requires adding only water is the easiest way to use a stain poultice for stone.

How Does a Poultice Work?

Poultices are interesting in that they work to lift the stain from the stone by reversing the process that got the stain into the stone in the first place. The chemical in the material is delivered into the stone where it reacts with the stain. The material lifts the liquid from the stone. So the process is such that it draws the stain from the stone.

Using a Poultice to Remove Stains

A mentioned above, the simplest way to execute this method of stain removal is to get a premixed poultice from a stone maintenance supply source. That way you won't have to acquire and perfectly mix the components necessary for creating the poultice. Premixed solutions normally only require the addition of water. Here are the steps needed to properly use a poultice to remove stains from stone.

  1. Poultice Preparation: for powder, mix the cleaning chemical into a thick paste the consistency of peanut butter or, if paper soak in the chemical but don't allow the liquid to drip. Premixed poultice powders only require water.
  2. Stone Preparation: using distilled water wet the stained area to prepare it for the poultice.
  3. Poultice Application: add the poultice to the stained area that you just applied water to so that the poultice is in the range of 1/4" to 1/2" thick and be sure to extend the poultice beyond the edge of the stained area about 1 inch and make sure it is applied evenly.
  4. Covering the Stone and Poultice: using a piece of plastic, cover the entire area you applied the poultice to and tape the edges of the plastic down so it is completely sealed.
  5. Allow to Dry: allow the process to work and give the poultice time to thoroughly dry. This usually takes any where from 24 to 48 hours depending on conditions in the environment. The drying process is what lifts the stain from the stone and transfers it into the poultice material so this is an important part of the procedure. After about 24 hours, remove the plastic from the area and allow the poultice to dry.
  6. Remove the Poultice: remove the poultice from the stained area and use a plastic or wooden scraper if needed and rinse the stone with distilled water. Then dry with a clean soft cloth.
  7. Repeat Steps 1-6 if Necessary: some stains may require more than one iteration of this process to remove them and there are some stains that may never be completely removed, but using a poultice is a simple way to remove inorganic stains from metals.
  8. For Calcareous Stone: calcareous stone etches from acidic chemicals so if the stone is of this sort, you will need to remove the etch after taking the stain out of the stone.

Poultices are a good way to remove stains from natural stone. And as we mentioned earlier, some kinds of stains call for using a poultice on stone stains. At any rate, now you know how to remove stains using a poultice powder. Additionally, you have seen some potential pitfalls if you do not use the proper poultice material and chemical on the correct type of stone. Finally, you know that if you are working on a calcareous type of stone, you will need to treat the etch that is left behind once the stain is removed.