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How to use a grout pen

Updated: 21 October 2026

You have a pen in your hand, or you are about to buy one if the method looks manageable. How to use a grout pen comes down to a clean, dry joint, a nib that is flowing, a thin line, and a wipe before the excess sets. The pen coats sound grout. It does not fill a hole or seal a leak. The product table stays on the [Grout pen](/hub/flooring-tools-and-accessories/grout-pen) comparison. Colour and pack are in the [grout pen buying guide](/hub/flooring-tools-and-accessories/grout-pen/sub/grout-pen-buying-guide). Whether a shower is a fair place is the [grout pen shower](/hub/flooring-tools-and-accessories/grout-pen/sub/grout-pen-shower) page. Listings were captured on amazon.co.uk on 19 October 2026. Peter F. scored these listings, not a lab, and amazon.co.uk links may earn a commission.

You have a pen in your hand, or you are about to buy one if the method looks manageable. How to use a grout pen comes down to a clean, dry joint, a nib that is flowing, a thin line, and a wipe before the excess sets.

Our top picks

UniBond UniBond grout reviver pen, white, pack of 3

Best overall

UniBond UniBond grout reviver pen, white, pack of 3
8.7/10about £12.60
View offer
QHSXMQ QHSXMQ white grout pen, 8 with spare nibs

Best value

QHSXMQ QHSXMQ white grout pen, 8 with spare nibs
8.7/10about £5.99
View offer
DRTRU DRTRU white grout pen, pack of 5

Alternative

DRTRU DRTRU white grout pen, pack of 5
7.7/10about £9.99
View offer
On this page
  1. 1.Clean and dry the joint first
  2. 2.Prime the nib and draw a thin line
  3. 3.Dry times are not one number
  4. 4.When the pen will not work

Clean and dry the joint first

Paint on damp or greasy grout wipes off with the next clean. Homebuilding’s advice is sugar soap and at least two hours of drying. B&Q starts with soapy water, then a grout cleaner if stains remain. Skip chlorine bleach as the last step. Two hours is the wait before you paint, not a brand’s touch-dry time. A joint that still looks dark in the depth is wet. If the grout powders onto your cloth, stop. A leak into the ceiling below is a tiler’s job, which grout pen vs grout paint separates from a cosmetic coat. Keep the pen off silicone at a bath edge.

Prime the nib and draw a thin line

Shake the pen until the agitator rattles. Depress the nib on card until a controlled bead appears. UniBond’s method is to apply sparingly, wipe excess with a damp cloth, and add a second coat after one hour if you need it. Start vertical joints from the base and use a light hand. Press hard and the felt nib shreds, or the liquid pours. Wipe stray colour while it is wet. A dried drip, which Sinofort reviews mention, is much harder to lift. Cap the pen when you pause.
UniBond UniBond grout reviver pen, white, pack of 3

Testsieger

UniBond UniBond grout reviver pen, white, pack of 3
8.7/10about £12.60
View offer

Dry times are not one number

There is no single dry time. Homebuilding’s two hours is the wait before you paint, not after. UniBond’s listing and brand method point to about 60 minutes, with a second coat after one hour. Metro quoted the brand line that you can shower after 60 minutes. That is UniBond’s claim for that pen. DRTRU says touch-dry after 30 minutes and to allow two hours. Peaflew says bonded within two hours. QHSXMQ states no dry time. Do not copy UniBond’s 60 minutes onto a pack that never stated a time. If the carton is blank, leave the line until the next day before you soak it.

When the pen will not work

The repeated fault is flow that only happens with the pen pointing down. DRTRU reviews say walls are poor unless the liquid follows gravity. Flintronic reviews say horizontal lines are harder than vertical ones. If a shake and a depress on card produce nothing, the pen may have arrived dried out. That is a satisfactory-quality question under the Consumer Rights Act 2015, section 9, not a fault you fix by pressing harder. Some buyers poured the liquid out and used a brush. That workaround is not the method to start with. Stop and regrout when the grout powders or the same mould returns. Call a tiler when water appears in the ceiling below.

Common questions

How long must it dry before I draw?
Homebuilding says at least two hours after washing, and longer if the joint still looks damp in the depth. That wait is before the pen, not after it. In a bathroom that was used in the morning, give it the rest of the day with the extractor running. Painting a damp joint is the usual reason a waterproof line disappears at the next shower.
How do I start the nib?
Shake until the pen rattles, then depress or pump the nib on card until you see a small, even bead. UniBond and B&Q both use that sequence. Use light pressure on the joint, starting vertical lines from the base. If you have to press hard before anything appears, stop. Hard pressure is what shreds felt and dumps liquid onto the tile.
What if paint gets on the tile?
Wipe it at once with a damp cloth or a tissue, while it is wet. Flintronic buyers describe that as straightforward. Once a drip has dried, Sinofort reviews say it is difficult to remove, especially on narrow joints where the pen floods. Work one joint at a time so you are never discovering a dry smear three rows later.
When can I apply a second coat?
After the dry time printed for the pen you bought. UniBond’s method says one hour. DRTRU and Peaflew separate a 30-minute touch-dry from about two hours for the fuller result. A second coat is reasonable when the first looks thin, which AOOSU reviews needed on old bath stains. Do not recoat while the first pass is still wet, or you will drag it onto the glaze.
What if nothing comes out unless the pen points down?
That fault is common on DRTRU, Flintronic, and PEAKTOP in this review set. You can sometimes finish a vertical joint by keeping the nib downward, and horizontal joints stay awkward. If card-priming still gives nothing, treat it as dried out or faulty. Pouring the pen into a pot is something reviewers did after the nib failed. It is not the method to start with, and a dead pen on arrival is a return.
When should I stop and regrout instead?
Stop when the grout powders, tiles are loose, the same mould returns, or water is reaching another room. A pen hides colour on a sound joint for a while. It does not rebuild a joint or fix a leak. Black growth in silicone at a bath or tray is a sealant replacement, not a grout-pen job. Call a tiler for those, and keep the pen for firm, clean, glazed lines.

Related pages

Best grout pen

Grout pen

Grout pen buying guide: joint, colour, nib, and price

Grout pen shower: glazed walls, not the tray floor

Grout pen vs grout paint: pen, colourant, or new grout

Sources

Public UK sources used for this comparison. Listing prices, stars and review counts are the amazon.co.uk figures saved for these 12 ASINs on 19 October 2026.

  1. UniBond Triple Protection Grout Reviver Pen (retrieved 19 October 2026)
  2. UniBond label details via McGrocer (retrieved 19 October 2026)
  3. ASDA: UniBond grout reviver pen 7 ml (retrieved 19 October 2026)
  4. Consumer Rights Act 2015, section 9 (retrieved 19 October 2026)
  5. HSE: Treated articles (retrieved 19 October 2026)
  6. Bromley Tilers: How to clean grout (retrieved 19 October 2026)
  7. Homebuilding: Cleaning grout (retrieved 19 October 2026)
  8. Ideal Home: Grout colouring with a grout pen (retrieved 19 October 2026)