Blue or red chalk line
Updated: 22 October 2026
You are about to load a reel for plaster, timber, a concrete floor, or an outside wall, and the red bottle looks clearer in the photo. Blue or red chalk line is a permanence question, not a brightness contest. Blue is the general mark you may still wipe or paint. Red is the mark trade sources treat as permanent, including outdoor work that rain would clear a temporary powder from. Peter F. used UK manufacturer pages and trade guides, plus the bottles named on the amazon.co.uk listings in this set. There was no lab test of bleed-through. A qualifying purchase can earn a commission at no extra cost to you. The rows are on the [chalk line comparison](/hub/measuring-and-marking-tools/chalk-line).
You are about to load a reel for plaster, timber, a concrete floor, or an outside wall, and the red bottle looks clearer in the photo. Blue or red chalk line is a permanence question, not a brightness contest.
You are about to load a reel for plaster, timber, a concrete floor, or an outside wall, and the red bottle looks clearer in the photo. Blue or red chalk line is a permanence question, not a brightness contest. Blue is the general mark you may still wipe or paint. Red is the mark trade sources treat as permanent, including outdoor work that rain would clear a temporary powder from. Peter F. used UK manufacturer pages and trade guides, plus the bottles named on the amazon.co.uk listings in this set. There was no lab test of bleed-through. A qualifying purchase can earn a commission at no extra cost to you. The rows are on the chalk line comparison.
Our top picks
| Badge | Product | Chalk colour | Chalk in the box | Line length | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Milwaukee Milwaukee chalk reel, 100 ft | Red on the ink-colour field | Not stated in the spec fields | 100 ft | 8.9 | about £17.47 | View offer |
| Alternative |  PRESCH PRESCH chalk line, 30 m | Red | 150 g red | 30 m | 8.4 | about £21.99 | View offer |
| Best value |  OX OX Trade chalk reel, 30 m | Blue | 118 ml blue | 30 m | 8.0 | about £12.00 | View offer |
Colour is permanence
Visibility and removal are different problems. A pale snap is usually a dry cord, a long pull that was not rewound through the chamber, or a line too fine for the surface. The fix is another pass of a suitable powder, or a bolder cord, not a switch to red because red looks stronger in the tub. How to coat and snap the cord is on how to use a chalk line. Wonkee Donkee describes blue as temporary and general, and red as permanent and suited to outdoor work that rain would wash a temporary colour from.
That permanence is also the risk. Snap red across plaster you still have to emulsion, and you may be looking at a line paint does not hide. IRWIN’s UK help page says to keep permanent red, and permanent black, off finish material. We will not say red always bleeds through every paint, because there is no lab panel here. Choose it where the mark will be covered, cut away, or left on exterior masonry. If a week of weather is not enough for your blue, the permanent colours are the next decision.
Blue and white
Blue is the default for interior layout and for a mark you expect to lose. Stanley’s UK page for its own 115 g blue refill calls blue an all-round chalk, states weatherability of about a week for that product, and points red at external masonry and white at interior work. That week is Stanley’s claim for Stanley’s blue, not a promise for the 118 ml in the OX Trade pack or the powder with the Tolsen reel. If your blue washes off in a shower, that matches “temporary”. A second snap of the same blue will not make it weatherproof.
White sits beside blue indoors, where a strong blue would show on a light surface you are not painting straight away. Use white or blue when the line is a guide for a cut you will make soon, or for a wall that still has to look clean. If the same line has to survive rain on blockwork, blue’s short weather window is the reason to read the red bottle before you fill the reel.
Red and black
Choose red when the mark must outlast weather, or when the surface will hide it. Stanley’s UK page puts red on external masonry. IRWIN, answering a rainy-season question, points to permanent red or black and still says to keep those colours off finish material. Black is in that same permanent class. It is not a milder indoor substitute. Treat it as you would treat red: acceptable on exterior masonry or on a surface that will be covered, a problem on plaster and joinery you will paint.
Kennedy’s marking-chalk sheet adds a stain caution and states there is no DIN or any other standard for this use. There is no British Standard number for “red means permanent” either. Do not claim these bottles were tested against the 0.1 mg/m³ respirable crystalline silica limit in EH40/2005. No measurement of these tubs was found. If you have already snapped red on plaster, stop adding more of the same powder. A line that ghosts through paint is a decorating problem, not a cue to snap harder.
What this set actually includes
Read the bottle in the listing before you treat every reel as red or blue. OX Trade, OX-T630602, includes 118 ml of blue at about £12.00. Tolsen 42012 includes blue powder at about £10.77. Rolson lists blue chalk. The OX Pro style name includes a blue refill. PRESCH, at about £21.99, is the pack that clearly includes red: 150 g on a 30 m reel. That makes it the red option in this set, at the highest price, not the default interior reel.
Milwaukee 48-22-3986 is the awkward row. The material field says red chalk, and a bottle is not in the specification fields, so the parcel is not a confirmed red refill. If you add your own powder, you choose the colour. OX Contractor states that powder is not included, which at least makes the colour your decision. A title that only says “chalk” has not told you whether the mark will wipe off before you paint.
Common questions
Will red chalk show through emulsion?
It may, and you should assume that risk on a wall you will paint. IRWIN’s UK help page says permanent red should stay off finish material. This page does not claim a lab result for every emulsion. Wonkee Donkee and Stanley’s UK notes class red as permanent, unlike general blue. If the plaster is still to be decorated, load blue or white.
Does blue chalk survive a shower on a roof?
Treat blue as temporary. Stanley’s UK page states about a week of weatherability for its own 115 g blue refill, which is not a figure for every blue bottle. Wonkee Donkee describes red as the colour for outdoor work that rain would clear a temporary powder from. A shower that removes the line is what temporary chalk does. Snapping the same blue again does not turn it red.
When is white the right powder?
White is the interior option when a blue line would show on a light surface you are not covering immediately. Stanley’s UK page points white at interior work, beside red for external masonry. It can still smudge, and it is not a promise that every white listing matches Stanley’s refill. Use it inside. Do not expect it to hold on an exposed wall through a wet week.
Is black chalk the same as red?
For this choice, yes. IRWIN groups permanent black with permanent red and says to keep both off finish material. Black is not a mild indoor colour. Use it where you would accept a mark that stays, and keep it off plaster you still have to decorate. There is no British Standard that grades these colours.
Can I snap blue twice if I cannot see it?
Yes, if the colour is right and the first snap was thin. Prime the cord, or rewind a long pull through the chamber, and snap once more on the same line. A second snap beside the first leaves a wide mark. Do not cure a pale blue line by loading red onto plaster. Visibility is a cord problem. Permanence is a colour problem.
Which reels in this set include red?
PRESCH includes 150 g of red chalk, at about £21.99 for a 30 m reel. That is the clear red pack. Milwaukee’s material field mentions red, and the bottle is not in the spec fields, so do not count it as included. OX Trade and Tolsen include blue. The OX Pro style name includes a blue refill. OX Contractor states that powder is not included.
Is there a British Standard for the colour?
No British Standard for chalk-line colour showed up in the sources used here. Kennedy’s data sheet says there is no DIN or any other standard for this use. The colour practice here comes from trade guides and from Stanley and IRWIN pages, not from a BS number on the tub. A reel without a standards mark is normal in this category.
Related pages
Sources
Public UK sources listed below, then the stored amazon.co.uk listings for these eleven reels. Prices are the stored shelf prices, not a live ticker.
- Wonkee Donkee Tools, what a chalk line is (retrieved 22 October 2026)
- Wonkee Donkee Tools, chalk colours (retrieved 22 October 2026)
- STANLEY UK, blue chalk (retrieved 22 October 2026)
- IRWIN UK help, chalk in wet weather (retrieved 22 October 2026)
- Kennedy marking chalk, product data (retrieved 22 October 2026)
- HSE EH40/2005, workplace exposure limits (retrieved 22 October 2026)
- HSE CIS36, construction dust (retrieved 22 October 2026)
- OX Tools UK, chalk reels and powder (retrieved 22 October 2026)