Added text to abrasive section

science-of-cleaning.tex

@@ -412,6 +412,24 @@ Surfactants are one of the most widespread and commercially important chemicals.
 
 \paragraph{Scrub-a-dub-dub}
 
+Unlike acids, bases, and surfactants, abrasives use physical means, rather than chemical means, to get something clean. In the home, you have seven basic options for abrasive cleaning:
+
+\begin{enumerate}
+\item Scrapers—can be metal or plastic
+\item Brushes
+\item Scouring pads
+\item Steel wool
+\item Cleansing powders
+\item Salt of baking soda
+\item Sand
+\end{enumerate}
+
+The danger with using any sort of abrasive cleaning technique is that it is all too easy to damage whatever you are cleaning. Steel scrapers may work great, but if the steel in your scraper is harder than the material you are scraping, you stand a very good chance of damaging the item.
+
+Abrasive cleaning usually works best (and lessens the potential damage to your item) when you combine it with other cleaning techniques. Soaking something in warm water will often help loosen material, making the scraping part of cleaning either easier or completely unnecessary. 
+
+This is why two of these methods—steel wool and cleansing powders—typically include a detergent, which helps to both loosen dirt and grime, but also helps to carry it away when you get to the rinse stage. 
+
 
 \chapter{Heat}