One of my favorite ways to add drawings to pottery is with AMACO Underglaze Chalk Crayons.
They feel much closer to drawing on paper than painting with underglaze. You can make loose lines, build up marks, change pressure, and leave some of the texture of the crayon visible after firing.
I’ve been using them on my handbuilt pieces for a while, and through testing I’ve found a firing process that gives me much more consistent results at cone 6.
The most important thing I learned: not every color behaved the same way under clear glaze.
Here is exactly how I use them, which colors have worked best for me, and what I changed when some of the crayons caused the clear glaze to develop a pebbled surface.
What are underglaze crayons?
Underglaze crayons are ceramic decorating materials that let you draw directly onto a ceramic surface much like you would with a traditional crayon or pastel.
Unlike regular crayons, the color is designed to survive firing.
AMACO calls these Underglaze Chalk Crayons, and they can be used to create lines, sketches, shading, and more graphic marks on ceramic surfaces.
What I like about them is that the result still feels drawn by hand.
A brush tends to create a fluid painted line. A crayon gives me something drier, more immediate, and slightly imperfect.
That quality is exactly what I want in my work.
I apply the crayons after bisque firing
For my process, I first make the piece and bisque fire it completely.
Once the piece is bisqued and clean, I draw directly onto the surface with the underglaze crayon.
I prefer working on bisque because the surface is firm and gives me something that feels much closer to drawing on paper.
It also means I can handle the piece freely while I work without worrying about damaging greenware.
My basic process is:
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Build the piece.
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Let it dry completely.
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Bisque fire.
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Draw on the bisque with the underglaze crayons.
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Add a clear glaze.
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Fire to cone 6.
That is the simplest version.
But through testing, I discovered that a few colors needed one extra step.
What happened when I glazed directly over the crayons
When I first started testing the crayons, I drew on the bisque and applied clear glaze directly over the drawing.
Some colors worked beautifully.
Blue, green, and brown gave me clean results with the clear glaze and fired well at cone 6.
But with some of my light blue and black tests, the clear glaze developed a pebbled, uneven surface over the crayon marks.
The rest of the glaze could look smooth while the areas over those crayon lines behaved differently.
That told me the issue was connected to the material in the crayon rather than the clear glaze alone.
The extra firing step that helped
For the colors that gave me trouble, I changed the process.
After drawing on the bisque, I did a low firing before applying the clear glaze.
My goal was to burn away the waxy binder in the crayon before putting glaze over it.
After that firing, I applied the clear glaze and fired the piece again to cone 6.
That solved the pebbled glaze issue in my tests.
So now I treat the colors differently depending on what I’ve already learned from testing them.
For the blue, green, and brown crayons that have behaved well for me, I can draw on the bisque, glaze, and fire.
For colors like the light blue and black that caused problems in my studio, I add the extra low firing before glazing.
This is based on my own kiln, clay, glaze, and application, so I would still recommend making test tiles before committing to an important piece.
Ceramic materials can behave differently depending on the full combination you are using.
My firing sequence
For the colors that have worked well without an extra firing:
Bisque → underglaze crayon → clear glaze → cone 6
For colors that caused the glaze to pebble:
Bisque → underglaze crayon → low firing → clear glaze → cone 6
That extra firing adds time, but for me it is worth it if it gives me a smoother clear surface.
The clear glaze I use
Most of the pieces shown here were glazed with Standard Ceramic 1125 Clear and fired to cone 6.
Standard lists 1125 as its clear glossy glaze, and it is a glaze I have used successfully over these drawings.
I’ve also had very good results with AMACO HF-9 Zinc-Free Clear.
AMACO specifically recommends HF-9 for use over underglazes because the zinc-free formula helps reduce certain color shifts, particularly with some green underglazes. It fires in the mid- to high-fire range and is designed for cone 5–10.
For this kind of surface decoration, a clear glaze is doing two things:
It gives the finished piece a glossy ceramic surface, and it lets the drawing stay visible underneath.
That means the quality of the clear matters almost as much as the crayon itself.
How I draw with the crayons
I use the crayons almost exactly as I would use drawing materials on paper.
I don’t try to hide the texture.
I like seeing:
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changes in pressure
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broken lines
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overlapping marks
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areas where the crayon catches more strongly on the bisque
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places where the drawing becomes lighter or darker
You can make a very controlled line, but personally I think these materials are most interesting when you let them still look like a drawing.
In the first reel below, I’m drawing with the blue underglaze crayon so you can see the pressure and line quality up close.
[BLUE CRAYON REEL]
In the second reel, I use the green crayon and show the same process on another piece.
[GREEN CRAYON REEL]
Both pieces were finished with clear glaze and fired to cone 6.
Does the crayon color change after firing?
Yes, it can.
Like most ceramic colorants, the unfired color is not always an exact preview of what you will see after firing.
Clear glaze can also affect how the color reads.
Some colors become deeper.
Some become brighter.
Some lines soften slightly under the glaze.
And depending on your clear glaze, clay body, firing temperature, and thickness of application, the final result may differ from mine.
This is why I keep coming back to the same advice: test first.
A small tile can save an entire finished pot.
Can you put clear glaze over underglaze crayons?
Yes, but test the exact combination you plan to use.
AMACO shows its underglaze chalk crayons being used in conjunction with glaze, and its other underglaze products are also commonly used underneath transparent glaze.
In my own cone 6 tests, clear glaze worked beautifully over several of the crayon colors.
But I also found that some colors affected the surface of the glaze unless I gave the decorated bisque an additional low firing first.
That is why I don’t assume every color in the same box will behave identically.
I test them individually.
Why I like underglaze crayons for handbuilt pottery
The thing I enjoy most is the contrast between a very dimensional clay form and a very simple drawn line.
Handbuilding already leaves evidence of the hand.
The crayon adds another layer of that.
It doesn’t feel printed or perfectly painted.
It feels drawn.
And because the drawing becomes permanent through firing, something that initially feels as casual as sketching with a crayon becomes part of the ceramic surface.
That combination still feels slightly magical to me.
My tips for using underglaze crayons
If you are experimenting with them for the first time, these are the things I would pay attention to:
Work on a clean bisque surface.
Dust can interfere with both the drawing and the glaze.
Test each color separately.
Do not assume every crayon will interact with your glaze in exactly the same way.
Test your clear glaze too.
The same drawing can look different underneath different clear glazes.
Keep track of your firing sequence.
If one color causes surface problems, test whether an additional firing before glazing changes the result.
Do not judge the final color before firing.
Ceramic materials transform in the kiln.
Write everything down.
Crayon color, clay body, clear glaze, firing temperature, and result. A small test library quickly becomes one of the most useful tools in the studio.
Frequently asked questions
How do you use AMACO underglaze crayons?
I apply AMACO Underglaze Chalk Crayons directly to a clean bisque-fired piece, then cover the drawing with clear glaze and glaze fire it. Depending on the color, I sometimes add an additional low firing between drawing and glazing.
Can you use underglaze crayons on bisque?
Yes. Bisque is my preferred surface because it is firm and easy to draw on.
Can you put clear glaze over underglaze crayons?
Yes. I have had good results using clear glaze over the crayons, but I recommend testing your exact crayon, glaze, clay, and firing combination first.
What clear glaze do I use over underglaze crayons?
For the pieces shown here I used Standard Ceramic 1125 Clear. I have also had excellent results with AMACO HF-9 Zinc-Free Clear.
Can underglaze crayons be fired to cone 6?
I have successfully fired my decorated pieces to cone 6. AMACO also shows its underglaze chalk crayons being used alongside products and techniques suitable for mid-range firing, though results can vary by color and glaze combination.
Why did my clear glaze become bumpy over the crayon?
There can be several causes of an uneven glaze surface, so I would not assume the crayon is always responsible. In my own tests, however, the problem appeared only over certain crayon colors. An additional low firing before glazing solved it for me.
Should I test every underglaze crayon color?
Yes. This is probably the most useful lesson from my own testing. Colors from the same product line can still behave differently once they are combined with your clay, clear glaze, and firing schedule.
The process is simple, but ceramics always has a way of reminding you that materials matter.
Bisque, draw, test, glaze, fire.
And keep notes.
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