Mayco Designer Liner is the product most potters mean when they ask for an "underglaze pen". It is a bottle of thick, clay-based color with a fine metal tip, so you can draw on a pot the way you would with a technical pen. This review covers what it is for, the colors and kit, the cone range, how to use the applicator bottle, and the problems people run into.
It is research-based. We worked from Mayco's Designer Liner line page, its color and kit pages, a Mayco project sheet, and US dealer listings, checked in October 2026. We have not used it ourselves, so performance claims are Mayco's.
Verdict
Designer Liner is the simplest way to get crisp, controlled lines on pottery at low fire or mid fire. Mayco rates it from cone 06 to cone 10 with little change, the tip comes ready to use, and the price per bottle is low. For lettering, outlines and pattern work, it is easier to control than a brush.
The trade-offs are that it clogs if you let it dry, cracks if you pile it on, and only comes in 10 colors. It needs a clear glaze for shine and for dinnerware. A single 1.25 oz bottle typically costs about $5 to $8 at US sellers in October 2026, and the 6-bottle kit about $25 to $35; check the live price.
Mayco Designer Liner spec table
| Spec | Mayco Designer Liner |
|---|---|
| Type | Clay-based, heavily pigmented line color with no frit |
| Colors | 10: SG-401 to SG-410 |
| Kit | DL-KIT3, six 1.25 oz bottles |
| Bottle | 1.25 oz squeeze bottle with threaded metal writer tip and a metal pin |
| Cone | Matures at cone 06/05, 1,828°F to 1,888°F (999°C to 1,031°C); fires up to cone 10, 2,381°F (1,305°C), per Mayco |
| Surfaces | Greenware, bisque, unfired glaze, glass (with a clear cap) |
| Finish | Matte without glaze; gloss under a clear |
| Labels | AP Non-Toxic per Mayco; ACMI seal shown on product pages |
| Dinnerware | Only under a compatible, durable clear or dinnerware glaze, per Mayco |
| Made in | US, per Mayco's product pages |
Source conflict: Mayco's line page says Designer Liner fires from cone 06 to cone 10 and shows cone 10 chips, while the BuyMayco and Sheffield Pottery listings say cone 06 to cone 6. Mayco also notes that cone 6 performance is printed on each label. If you fire to cone 10, check the label of each color and fire a test tile.
Is Designer Liner an underglaze?
In practice, yes. Mayco calls it "clay based and heavily pigmented", it contains no frit, it goes on before the glaze, and it fires matte unless a glaze covers it. That is how an underglaze behaves. Mayco also says Designer Liner "works great with Fundamentals Underglazes".
The difference is the job. A jar underglaze is for color areas; Designer Liner is for lines. It is also not Mayco's dimensional product: Mayco says "Designer Liner is not a dimensional product", so it does not leave raised lines after firing. For the basics of underglaze, see how to use underglaze.
Designer Liner colors and the kit
| Code | Color | In DL-KIT3 |
|---|---|---|
| SG-401 | Black | Yes |
| SG-402 | White | Yes |
| SG-403 | Red | Yes |
| SG-404 | Blue | Yes |
| SG-405 | Green | No |
| SG-406 | Brown | Yes |
| SG-407 | Yellow | No |
| SG-408 | Orange | No |
| SG-409 | Bright Green | Yes |
| SG-410 | Bright Blue | No |
Mayco shows chips at cone 06, cone 6 and cone 10 for each color. On the Black and Orange pages, the cone 6 oxidation chip is marked "No color change". Mayco does not publish written cone 10 notes on the color pages we checked.
How to use the Designer Liner applicator bottle
Mayco's instructions are short, and following them closely avoids most problems.
- Prepare the bottle: remove the white cap and gently puncture the plastic tip with the metal writer tip. Do not cut the plastic tip or widen the hole beyond the metal tip.
- Fit the tip: the metal writer tip threads onto the plastic screw cap.
- Start the flow: shake the bottle so color settles into the tip, then squeeze a little onto a paper towel.
- Draw: use steady, even pressure and keep the line thin. Practice on a spare tile first.
- Clean as you go: wipe the tip on a damp sponge every few minutes.
- Let it dry: allow the lines to dry fully before brushing clear glaze over them.
- Store it: put the metal pin in the tip, or swap back to the white plastic tip, keep air out and store at room temperature.
Mayco also suggests brushing Designer Liner to get "watercolor or ink wash effects", or using a fine liner brush for brushwork outlines. A tile and a #10/0 liner brush help with extra-fine detail, per BuyMayco. Our pottery brushes guide covers liner brushes.
Surfaces and glazes it works with
Mayco lists greenware, bisque, unfired glaze, and glass (with a clear cap over it). It can go on top of a non-moving glaze or under a sheer or semi-transparent glaze. The key rule is movement: Mayco warns that "design work could be distorted when applied on top of moving glazes", and asks for "a non-moving translucent or clear glaze over the top" to keep lines sharp.
Mayco's own stoneware plate project shows the usual order: Black Designer Liner straight on cone 04 bisque, two coats of SW-001 Stoneware Clear over it, fired to cone 5/6. A runny glaze such as Copper Float went only on the rim and back, away from the lines. See our clear glaze guide for non-moving clears.
Clear glaze, matte finish and dinnerware
Without glaze, Designer Liner fires matte and slightly textured. Mayco says that texture can trap bacteria, and that a clear is needed for gloss. For pieces that touch food, Mayco says to cover it with a compatible clear or other dinnerware glaze that is chemically durable, free of surface texture and meets FDA guides CPG 545.400 and 545.450, and that makers selling ware are responsible for testing it.
Dealer wording varies: BuyMayco calls it "Certified AP Non-toxic and Food Safe" yet says it "may not be suited for dinner ware due to surface characteristics". Treat bare Designer Liner as decorative only, and see our food safe glaze guide. Read Mayco's SDS for each color before use.
Common problems and fixes
The tip keeps clogging
Designer Liner is clay based and dries fast in narrow passages, Mayco says. Wipe the tip on a damp sponge often, push the pin through to clear it, keep the pin in when you stop, and soak the metal tip in warm water to remove dried residue.
Lines crack or pop off after firing
Mayco explains this directly: "Since there is no frit, designer liner will crack or pop off when over applied." Draw thinner lines and do not build them up for a raised effect.
The color dried in the bottle
Add a few drops of water at a time, stir and test the thickness. Mayco warns against over-thinning, which gives weak, spreading lines.
Lines blurred in the glaze firing
The glaze over them moved. Use a non-moving clear, keep fluid glazes away from the design, and fire to the clear's stated cone.
What Designer Liner does well
- Pen-like control for lines, dots and lettering.
- One product from cone 06 to cone 10, per Mayco, with little color change at cone 6 on the colors we checked.
- Low cost per bottle, and a 6-color kit.
- Works on greenware, bisque and unfired glaze.
- Clear, practical maker instructions.
Weak points
- Only 10 colors, with no pastels.
- Clogs if left open or unused.
- Cracks when applied thickly; not dimensional.
- Matte and textured without a clear; not for food contact bare.
- Dealers disagree with Mayco on the top cone.
- Replacement tip part numbers are not published by the maker.
Who should buy it, and who should skip it
Buy Designer Liner if you want lettering, outlines, pattern grids or dot work on pots fired anywhere from cone 06 to cone 6, and you are happy to put a clear over it. It suits beginners too, because a squeeze bottle is easier to steady than a liner brush.
Skip it if you want soft, shaded drawing (a pencil does that better), raised dimensional lines, or large color areas. Skip it also if you only glaze with runny, reactive glazes, which will smear the lines.
Mayco Designer Liner bottle
A single bottle is the place to start: Black SG-401 for lettering and outlines on light clay, or White SG-402 for lines on dark clay. Each bottle includes the metal tip and pin.
- Size: 1.25 oz
- Cone: 06 to 10, per Mayco
- Finish: Matte bare, gloss under clear
Pros
- Low cost
- Ready-made fine tip
- Wide firing range
Cons
- Clogs if left to dry
- One color per bottle
Who should skip it: Anyone who wants shaded drawing rather than lines.
Mayco Designer Liner Kit DL-KIT3
The kit bundles Mayco's six best-selling colors: Black, White, Red, Blue, Brown and Bright Green. It covers the colors most people use for outlines and lettering, with black for light clay and white for dark clay.
- Contents: 6 x 1.25 oz bottles
- Colors: SG-401, 402, 403, 404, 406, 409
- Cone: 06 to 10, per Mayco
Pros
- Six colors in one buy
- Includes black and white
Cons
- No yellow, orange or bright blue
- Bottles can dry before you use them all
Who should skip it: Potters who only need black for lettering.
Alternatives
- Underglaze pencils: dry pencils for shading and soft lines.
- Mayco Fundamentals underglaze: jar underglazes for color areas, often paired with Designer Liner.
- Mayco Stroke and Coat: low-fire color that fires glossy without a clear.
- Best underglazes, compared across brands.
Sources: Mayco Designer Liner line page, Designer Liner product category, product pages for SG-401 Black and SG-408 Orange, DL-KIT3 Designer Liner Kit page and the Designer Liner Stoneware Plate project (maycocolors.com); BuyMayco SG-401 listing; Sheffield Pottery and Mayco Paint Store Designer Liner pages; School Specialty DL-KIT3 listing (kit price band). Research-based, not hands-on. Specs checked October 2026.