Toolipedia: Marking Chalk

What is marking chalk?

Chalk is a form of limestone and is mined, crushed and processed into a dry powder. A dye is added to create marking chalk. Marking chalk is used with chalk lines to mark straight lines on flat surfaces between two points. Chalk lines were first known to be used by the ancient Egyptians.

How is marking chalk used?

A chalk-covered string is stretched the desired distance and pulled taut. With both ends laid flat on the surface, the string is pulled up and then let go, causing it to snap back onto the surface, depositing the chalk in the process.

Marking chalk used in chalk lines is often used by carpenters, siders, roofers and other tradespeople who need to mark long, straight lines.

What are the different types of marking chalk?

There are eight main colors of marking chalk, each with a different property and designed use.

Light Violet for temporary lines indoors

• Remodeling
• Interior trim
• Interior decorating
• Cabinet installation

Blue and White are standard for indoors and out

• Roofing
• Siding
• Paneling
• Interior layout

Orange, Green and Yellow for high visibility outdoors

• Corrections
• Plumbing and electrical
• Roofing
• Masonry

Black and Red for permanent lines

• Exterior layout
• Concrete layout
• Roofing
• Steel and metal fabrication

What makes a good marking chalk?

Irwin has been making chalk for a long time and is a trusted brand.

Chalk Tip

If you pull out a bunch of string before you refill, there will be more room for chalk and the first time you use the string, it will be fully saturated in chalk and produce a nice, clear line.

Click here for more chalk tips.