Four synthetic round brush ranges that sell below £30 a brush in the UK, compared by fibre, size range, published head dimensions, stated purpose and where to buy them.
If you are looking for the best watercolour brushes under £30, the useful first question is not which brand to trust but which kind of round suits the way you paint. This page sets four inexpensive synthetic ranges side by side so you can compare their published specifications before you hold one in a shop.
At a glance
Choose by stated purpose first. Princeton Aqua Elite is made as a synthetic alternative to Kolinsky sable. Princeton Neptune is made as a synthetic alternative to squirrel hair and is the softer of the two on Princeton’s own stiffness scale. Pro Arte Polar and the Cass Art Artists’ Synthetic Brown round are general purpose nylon and synthetic rounds at the lowest listed prices here.
Size numbers do not compare across ranges. A Princeton Aqua Elite size 8 and a Princeton Neptune size 8 have different published head dimensions, even from the same maker. Compare the measurements where a maker publishes them.
All four are synthetic. Names such as “synthetic Kolinsky” and “synthetic squirrel” describe the hair the fibre is meant to imitate. They do not mean the brush contains natural hair.
Check the point and the ferrule yourself, or know the returns policy. A specification cannot tell you how an individual brush behaves. If you can, wet the head in the shop; if you buy online, read the retailer’s returns terms first.
Keep a separate inexpensive brush for masking fluid. Masking fluid can be difficult to remove from fibres, so many painters keep a spare round for it rather than using their main brush.
The four ranges compared
The table uses the makers’ own figures where they publish them. Prices are listings, not offers, and they change; recheck before you buy.
| Range | Fibre, as described | Round sizes published | Published head size, round 8 | Maker’s stated purpose | UK listing checked |
|---|---|---|---|---|---|
| Princeton Aqua Elite, Series 4850 | Synthetic, made as a Kolinsky sable alternative | 12/0 to 20 (maker) | 23 mm long, 4.85 mm wide | Watercolour; Princeton rates it 5 of 5 for watercolour and 2 for stiffness | Jackson’s: rounds 3/0 to 16, £5.60 to £18.00 before temporary discounts (20 October 2026) |
| Princeton Neptune, Series 4750 | Synthetic, made as a squirrel hair alternative | 0 to 20 (maker) | 20 mm long, 4.75 mm wide | Watercolour; Princeton rates it 5 of 5 for watercolour and 1 for stiffness | Jackson’s: rounds 0 to 20, £5.60 to £26.50 (20 October 2026) |
| Pro Arte Polar White Nylon, Series 31 | White nylon | 0000 to 20 (maker) | Not published in the sources checked | Water based paints; positioned for students and beginners | Cass Art: from £2.30 (20 October 2026) |
| Cass Art Artists’ Synthetic Brown, short handle round | Synthetic brown fibre | Assorted; no size table published | Not published | Watercolour and gouache; listing also names acrylic and oil | Cass Art: from £2.95; size 8 £9.95 (20 October 2026) |
Princeton’s stiffness figures are the maker’s own scale, where a lower number means a softer head. They are useful for comparing the two Princeton ranges with each other. They do not translate to brushes from other makers.
Notes on each range
Princeton Aqua Elite
Aqua Elite is Princeton’s synthetic answer to Kolinsky sable, and the maker describes it in strong terms, including “better than natural Kolinsky”. That is a manufacturer claim. What the specification does show is a wide run of round sizes, from very small detail rounds to a size 20, and a published head length and width for each, which makes it easier than usual to choose a size by measurement. Of the four, it is the range aimed most directly at painters who want one general watercolour round, and Princeton rates it firmer than Neptune.
Princeton Neptune
Neptune is Princeton’s synthetic squirrel range, rated softer than Aqua Elite on the maker’s scale and described by Princeton as its “softest and thirstiest” synthetic. Squirrel style heads are usually chosen for laying washes rather than for fine detail, so this is the range to look at if your work leans towards broad, wet passages. Treat any comparison of water capacity as the maker’s description until you have used one.
Pro Arte Polar White Nylon
Polar is a white nylon round from Pro Arte, positioned by the maker and its retailers for students, beginners and general water based painting. Its size run reaches down to 0000 and up to 20, and it has the lowest listed entry price here. That makes it a practical way to try an unfamiliar size before spending more, or to keep a spare for masking fluid.
Cass Art Artists’ Synthetic Brown
This is Cass Art’s own brand synthetic round. The listing gives a starting price and the fibre type but no head dimensions, and the product page contradicts itself on handle length, so check the specific size you want before ordering. Its value here is availability: Cass Art has shops in several UK cities, so it is one of the easier brushes to see in person.
Why the size number is not enough
Brush size numbers are set by each maker. Within Princeton’s own published figures, an Aqua Elite size 8 is 23 mm long and a Neptune size 8 is 20 mm long. Across makers the gap can be larger, and some makers do not publish dimensions at all. If you are replacing a brush you already like, measure its head and compare that rather than the number. The guide to watercolour brush sizes explains how to read size numbers across ranges.
What to check before you buy
A specification narrows the choice. It cannot tell you how the brush in your hand will behave. Before you commit, check what you can:
- The point. In a shop that allows it, dip the head in water and see whether it comes to a clean point without stray fibres.
- The ferrule. It should be firmly crimped, with no movement between ferrule and handle.
- The head shape. Look for fibres that are evenly set and not splayed from packing.
- The returns policy. If you are buying online, know whether an unused brush can be returned before you order several sizes.
Individual brushes vary within any range, which is another reason a dated listing is only a starting point.
A practical starting choice
If you want one round for general watercolour work, start with the range whose stated purpose matches your work. Aqua Elite is made as a general watercolour round and is rated firmer than Neptune on Princeton’s scale; Neptune is made as a softer wash round. Choose a size by the published head length that suits the scale you paint at, not by the number alone.
If you want a low cost first brush, a spare, or a dedicated masking fluid brush, Pro Arte Polar and the Cass Art synthetic round are the two lowest listed entry prices here. Either lets you try a size before buying it again in a dearer range.
The comparison of Kolinsky sable and synthetic brushes sets out how the two fibre families differ. For more pieces like this one, see the Reviews section, and for retailers, the UK watercolour suppliers guide.