Irwin 4935518 Permanent Marking Chalk 6 Oz Indigo Blue

Product Description

The IRWIN INDUSTRIAL TOOL CO 4935518 is a 6-ounce fill of Strait-Line permanent marking chalk formulated for demanding outdoor conditions. The indigo blue pigment delivers a permanent staining action that remains visible after weeks of weather exposure and jobsite wear. This chalk is engineered to resist harsh weather without requiring a spray sealant over the line, making it a practical choice for exterior layout work on rough or porous surfaces. Licensed contractors, framers, and trade professionals who work outdoors in variable weather conditions use this chalk where a standard, washable chalk would fail to hold.

This chalk refill is suited for exterior framing, masonry layout, roofing, and concrete flatwork where the snap line must remain readable through rain, UV exposure, and repeated foot traffic. Its permanent staining characteristic means it bonds to surfaces including concrete, brick, wood, and similar substrates. It is packaged as a single 6-ounce unit and is compatible with standard chalk line reels that accept powdered chalk refills. It is particularly useful on jobs requiring layout lines to stay intact across multiple work sessions without re-snapping.

Key Features

• Permanent staining formula — line remains visible after weeks of outdoor weather exposure
• Indigo blue pigment for high contrast against common construction surfaces
• Eliminates or reduces the need for spray sealant over snapped lines
• Formulated for extreme outdoor conditions including rain and prolonged jobsite wear
• 6-ounce fill size compatible with standard chalk line reels

Compatibility

Designed as a refill for standard chalk line reels that accept powdered marking chalk. Verify reel manufacturer fill-port size before use.

Installation Notes

Load chalk into the reel per the reel manufacturer instructions, avoiding overfilling the reservoir. Because this chalk stains surfaces permanently, test on an inconspicuous area before snapping lines on finished or decorative materials. Wear appropriate eye and skin protection when handling fine chalk powder in windy conditions. Do not use on surfaces where permanent marking is not acceptable.