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How to apply decorator's caulk

Updated: 23 October 2026

The skirting has a dark crack, and the last bead you painted cracked or sank into a screw hole. Decorator's caulk fails that way when the joint is too deep, still damp, or painted before a skin has formed. Acrylic dries because water leaves the paste, so a fat bead shrinks and a brittle matt film splits on top. A thin bead, tooled once, painted on the cartridge's own clock, is the method. Product choice stays on the [acrylic sealant comparison](/hub/fillers-adhesives-and-sprays/acrylic-sealant). This page assumes you already have an acrylic. A qualifying purchase through our links can earn us a commission at no extra cost to you.

The skirting has a dark crack, and the last bead you painted cracked or sank into a screw hole. Decorator's caulk fails that way when the joint is too deep, still damp, or painted before a skin has formed.

Our top picks

Soudal Soudal decorator caulk, white, pack of 2

Best overall

Soudal Soudal decorator caulk, white, pack of 2
8.8/10about £6.18
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Everbuild Sika Caulk Once white, pack of 2

Rank 2

Everbuild Sika Caulk Once white, pack of 2
9.2/10about £5.38
View offer
Everbuild Everbuild Everflex 175 acrylic sealant, white, 300 ml

Rank 3

Everbuild Everbuild Everflex 175 acrylic sealant, white, 300 ml
8.2/10about £6.20
View offer
On this page
  1. 1.Prepare the gap
  2. 2.Gun a bead that touches both sides
  3. 3.Tool once and do not drown it
  4. 4.Paint on the cartridge's clock
  5. 5.When this method is the wrong job

Prepare the gap

Both sides must be sound, dry and free of dust, loose paint and failed sealant. On very porous new plaster, the Sika approach is one part caulk to two parts water. Soudal's DIY cartridge caps the width at 10 mm and looks for a depth of at least about 5 mm. Wider than that, use a foam backer so the bead grips the two faces and not the back of the hole. Without it, a screw hole shrinks. Do not gun into rain, frost, or a substrate below about 4 °C to 5 °C. Class and interior or exterior are on the acrylic sealant buying guide.

Gun a bead that touches both sides

Cut the nozzle at about 45 degrees, no wider than the gap. Pierce the inner seal, seat the cartridge in a standard skeleton gun, and fill the nozzle before you touch the wall. Pull the gun towards you so the paste is pressed into both sides. Pushing a blob ahead of the nozzle leaves a bead that sits on the surface. For a skirting, one continuous pass is enough. At a corner, stop, tool, and start again. Ease the rod before you lift the gun. Coverage is only a rule of thumb.
Soudal Soudal decorator caulk, white, pack of 2

Testsieger

Soudal Soudal decorator caulk, white, pack of 2
8.8/10about £6.18
View offer

Tool once and do not drown it

Tool the bead while it is wet, then leave it. Pull the masking tape while the paste is still soft. Caulk Once gives about 20 minutes and says not to flood the joint. A soaked cloth adds water to a paste that has to dry, and the bead shrinks more. If the first bead missed one side, wipe it out and run it again. After cure, do not sand Caulk Once. If the joint is deeper than it is wide, the backer should already be in place.

Paint on the cartridge's clock

There is no single paint-in-15-minutes rule. Caulk Once: overpaint about an hour after a skin, full cure 3 to 5 days. The Amazon 15-minute cell is not the method. Soudal says paint when fully dry, and the paint has to be elastic enough. A thin fill paints sooner than a bead of 5 mm or more. Do not copy another product's oil-paint delay onto vinyl matt.

When this method is the wrong job

Stop if water sits on the joint. Decorator acrylic is not a shower or a bath rim. The sheets behind Caulk Once, Soudal and Everflex 175 exclude continuous immersion. That decision is acrylic against silicone. Stop if the sash has to open, if the gap is wider than 10 mm on the Soudal DIY pack, or if the joint is a floor, below ground or bitumen. Call a joiner if the frame is rotten or the sash needs re-hanging. A rash after skin contact, where a sheet warns of a preservative, needs medical advice.

Common questions

How do you cut the nozzle and load a standard gun?
Cut the nozzle at about 45 degrees so the hole matches the gap, then pierce the foil seal. Seat it in a standard skeleton gun and fill the nozzle before you start, on a piece of card if the first centimetre is air. A nozzle is not guaranteed: 151 and Everflex reviews include tubes without one, and one Soudal order had both nozzles snapped.
Should you push the gun or pull it?
Pull the gun towards you so the bead is forced against both sides. Pushing paste ahead of the nozzle leaves a bead that sits proud and does not wet the edges. Ease the rod before you lift off. On a long skirting, one pass beats a series of stops. At a corner, finish and tool, then start the next run.
When do you take the masking tape off?
Take it off while the bead is still wet, straight after you tool, so the tape does not tear a skinned edge. Leave it overnight and the skin rips with it. Caulk Once asks you to tool within about 20 minutes and not to drown the bead.
How long before emulsion, and why do sheets disagree?
Each sheet is one product. Caulk Once says about an hour after a skin, with full cure in 3 to 5 days. Soudal says paint when fully dry. Ignore an Amazon cell that calls 15 or 20 minutes a full cure.
What do you do with a gap deeper than it is wide?
Put a backer rod in so the sealant touches the two sides and not the back of the hole. Up to about 10 mm, depth can match width. Deeper than that, one pass shrinks in the centre. Caulk Once reviews say screw heads sink after repeated fills. If the width is over the cartridge maximum, change the detail rather than forcing the gun.
At what point do you stop and use a different product?
Stop when the joint stays wet, when the sash must move, when the gap exceeds the stated maximum, or when the background is bitumen, a floor or below ground. Soudal points a high-movement uPVC joint you also need to paint at a hybrid, which is not ranked here. Rotten timber or a sash that needs re-hanging is a joiner, not a thicker bead.

Related pages

Acrylic sealant for window frames

Acrylic sealant

Best acrylic sealant for a joint you will paint soon

Acrylic sealant buying guide: class, water and paint

Acrylic sealant vs silicone for paint or wet joints

Sources

Public UK sources used for this comparison. amazon.co.uk prices, stars and review counts were taken from the listings on 19 October 2026.

  1. Soudal Decorators Caulk technical data sheet (retrieved 19 October 2026)
  2. Soudal Decorators Caulk product page (retrieved 19 October 2026)
  3. Sika Caulk Once (retrieved 19 October 2026)
  4. Everflex 175 acrylic sealant data sheet (retrieved 19 October 2026)
  5. Soudal UKCA markings explained (retrieved 19 October 2026)
  6. 151 brown frame sealant safety data sheet (retrieved 19 October 2026)
  7. Acle Parish Council draught-proofing note (retrieved 19 October 2026)
  8. amazon.co.uk listings for the five ASINs in this set (retrieved 19 October 2026)