Check the listing for details. 1 Hydrion 0-13 Mechanical pH Pencil PEN Acid SURFACE Stucco Paint Testing Test. Condition: New. Listed at 14.75 USD. Photo and description are property and creation of and you shall find health and all rights reservedMADE in the USA Micro Essential Labs Hydrion Insta-Check 0-13 Mechanical pH Pencil Pen Acid Alkaline Surface Testing 1 Single Pen / Pencil Single - P-12M Single Hydrion Insta-Chek 0-13 Mechanical pH PencilEach pencil will give the user at least 100 tests.PRICE SHOWN IS FOR 1 PENCIL Product Description No technical training is necessary. To measure the surface pH just wet the surface with distilled water. Stroke the surface with the pencil. Wait approximately 30 seconds and compare the resulting color change with the color chart. This is considered a disposable pencil, there are no refills. The application will determine how long that the pencil lasts. pH is a measure of acidity and alkalinity. The pH scale goes from 0 to 14. At pH 7, the halfway point, there is a balance between acidity and alkalinity, the solution is neutral. The pH of a substance is a measure of its acidity just as a degree is a measure of temperature. A specific pH value tells the exact acidity. If the solution has excess acid, the balance is shifted so the scale reads a number lower than 7. (i.e. the greater the acid strength the lower the pH value) Similarly, a solution that is alkaline has a pH that is higher than 7 and the higher the alkali strength the higher the pH value (up to 14). Each unit on the pH scale actually represents a 10 fold difference in acid activity. Thus pH 4 is ten times as acidic a pH 5 solution. A pH 3 solution in turn has 10 times more acid than a pH 4 solution and 100 times the acid of the pH 5 solution. The pH scale of 0 to 14 is derived from the chemical properties of water. The pH scale cannot be used with other solvents such as alcohol, oils and other non-aqueous systems.