Plasterers mixing bucket: the water is not the bag
Updated: October 2026
A plasterers mixing bucket has to hold the powder as well as the water, with room to stir. The water for a 25 kg bag of finishing plaster is about 12 litres, and a 15 litre pail holds that water. The finished gauge does not fit. None of the nine listings in the [mortar bucket comparison](/hub/flooring-tools-and-accessories/mortar-bucket) is the tall tub trade catalogues rate at 35 litres. Sand-and-cement order sits on the [how to mix mortar in a bucket](/hub/flooring-tools-and-accessories/mortar-bucket/sub/mortar-bucket-how-to-mix) page. Listings were read on 19 October 2026, not a lab mix.
A plasterers mixing bucket has to hold the powder as well as the water, with room to stir. The water for a 25 kg bag of finishing plaster is about 12 litres, and a 15 litre pail holds that water.
A plasterers mixing bucket has to hold the powder as well as the water, with room to stir. The water for a 25 kg bag of finishing plaster is about 12 litres, and a 15 litre pail holds that water. The finished gauge does not fit. None of the nine listings in the mortar bucket comparison is the tall tub trade catalogues rate at 35 litres. Sand-and-cement order sits on the how to mix mortar in a bucket page. Listings were read on 19 October 2026, not a lab mix.
Our top picks
| Badge | Product | Capacity | Mixing claim | Type | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Best House Best House 14 litre builders bucket, pack of 4 | 14 litres (3 gallon) | Cement mixing and plastering named | Rigid builders bucket | 7.4 | about £13.99 | View offer |
 Faithfull Faithfull 15 litre flex tub, yellow | 15 litres | Named as a mixing tub | Flexible tub | 9.1 | about £7.04 | View offer | |
| Alternative |  M1SS M1SS 45 litre mixing tub, pack of 2 | 45 litres | Cement, plaster, and mortar | Wide mixing tub | 7.2 | about £21.99 | View offer |
On this page
Water is not the size of the mix
B&Q puts the water for a 25 kg bag of plaster at about 11–12 litres, poured in first. Refina's skim note says 11.5 litres of cold water, with the plaster into the water. A 14 or 15 litre bucket holds that water and still looks half empty. Tip the bag in and the gauge climbs the wall and leaves no room for a paddle. Buying 15 litres because that is the water is the usual mistake.
TDBS, Best House, Faithfull and Airflow are the 14 and 15 litre listings, for a partial gauge you can place. One Faithfull review already calls that flex tub too small for cement. A DIYUK reply suggests batches around 20–30 litres if you are new to the bag. That is experience, not a specification.
What trade tubs are sized for
Refina's X-1 chart states 35 litres for one 25 kg bag and 50 litres for two. The tub is described as tall HDPE so a thick mix splashes less. The cited price is £57.12 including VAT. It is a maker's bag rating, not a listing in this amazon set, and not a tested winner here. A single-bag claim on another seller's page does not transfer to a 15 litre pail.
For one full bag in one go, look for a tall tub, a stated bag rating, and freeboard. A wide shallow tub can show a similar litre number and still splash. British Gypsum's wording, via Refina, is to avoid over-mixing. This set stocks 14–15 litre pails, one 42 litre flex tub and two 45 litre tubs. The missing rung is 25–35 litres. The builders bucket size page keeps the general litre rules.
The 42 and 45 litre listings
The TDBS 42 litre flexi tub at £8.87 is the closest flex volume. The bullets name garden, feed, laundry and tools, not plaster, so a bag is not this listing's claim. Reviews mention splash and doubt heavy loads. There are no stated graduations, and online disagreement is not a specification for this ASIN.
The M1SS pair at £21.99 names plaster, cement and mortar, with two rope handles for a two-person lift, and 4.4 from 147 reviews. It is 300 mm high and 520 mm across, wide and shallow beside Refina's tall tub, with no lid and no volume marks. Do not walk a full tub alone. The single M1SS listing does not name plaster, and the title and catalogue disagree on the handle.
Clean water and a clean tub
Cold clean water goes in first, then the plaster, for a gypsum bag. That order is the opposite of a sand-and-cement gauge. Follow the bag if the litres differ from the 11–12 figure. Residue from the last mix shortens the next set. Refina's note, following British Gypsum, is that old plaster left in the bucket makes the new gauge go off sooner. Wash the tub, the paddle and the hawk as soon as you stop.
Gloves, eye protection and a dust mask are the controls when you tip the bag. A partial bag you can stir beats a full bag in a tub that is already splashing. Call a plasterer if you cannot place the gauge before it sets.
Common questions
How much water is in a 25 kg bag of finishing plaster?
B&Q cites about 11–12 litres, and Refina's skim note cites 11.5 litres of cold water, with the plaster added to the water. Follow the bag if it prints a different figure. That water fits in a 15 litre bucket. The powder plus the water does not, once you leave room to mix.
Will a 15 litre bucket hold the bag?
No. A 14 or 15 litre pail holds the gauging water and a partial mix. It does not hold a finished 25 kg bag of gypsum plaster. One Faithfull review calls the 15 litre flex tub too small for cement. Use a larger tub, with freeboard, if the whole bag has to go in at once.
Is a 42 litre flexi tub enough for one bag?
Not as a stated fact. Refina starts at 35 litres for one 25 kg bag in a tall rigid tub that is not in this set. The TDBS 42 litre bullets do not name plaster, and reviews mention splash and heavy loads. It is not sold as a one-bag plasterers' bucket.
Is a 45 litre rope tub a plasterers' bucket?
The M1SS pair names plaster and describes two rope handles as a two-person lift. It is 45 litres, wide and 300 mm high, with no volume marks. That is closer in litres than a 15 litre pail, and it is still not Refina's tall 35 litre tub. Do not carry a full tub alone.
Why do plasterers dislike flexi tubs for skim?
Forum plasterers say a flex tub splashes on a finish coat and that cheap flex tubs crack. They are talking about the soft, wide shape, often under other brand names, not a lab test of TDBS or Faithfull. The TDBS 42 litre reviews already mention splash. A taller tub keeps a thick mix inside.
Should I mix two bags at once?
No, if this is your first bag. Refina's chart puts two 25 kg bags at 50 litres, which none of these listings is. Mix a partial gauge in a bucket you can stir, wash it out, and mix again. Two bags in one tub is a plasterer's pace, not a learning pace.
Related pages
Sources
Public sources used for this comparison, with the amazon.co.uk listings read on 19 October 2026.
- HSE: cement and health risks (retrieved 19 October 2026)
- HSE CIS26: cement (retrieved 19 October 2026)
- HSE INDG143: manual handling at work (retrieved 19 October 2026)
- HSE: manual handling in construction (retrieved 19 October 2026)
- Airflow: Invincible 15 litre builders bucket (retrieved 19 October 2026)
- B&Q: how to mix plaster (retrieved 19 October 2026)
- Hanson: plastering sand data sheet (retrieved 19 October 2026)
- Refina: white plastic mixing tubs (retrieved 19 October 2026)