Verdict
Blue Nebula is worth buying if you raku fire and want one of Spectrum's copper glazes, whose color swings with the reduction you give it. It is not a stoneware glaze, not for kids' classes, and not for anything you eat or drink from. The bigger catch is information: Spectrum's own product page shows only the name, sizes and a label icon, so most firing guidance comes from line-wide raku instructions printed by Spectrum's dealers.
This review is research-based. We checked Spectrum's product page, raku category and 2026 price list, plus US dealer listings, in October 2026. We did not fire this glaze ourselves, and we found no written color description from the maker.
Which Blue Nebula glaze do you mean?
Several glazes share the word "nebula", and they fire at very different temperatures. Check the maker and code before you buy:
| Glaze | Maker and code | Firing | Food use |
|---|---|---|---|
| Blue Nebula (maker name "Nebula") | Spectrum 863, 850 series raku | Raku, below cone 06 | Not for dinnerware (all raku, per Spectrum) |
| Nebula Blue | Laguna MS-220 | Cone not published by Laguna; a European distributor lists 1,210°C (2,210°F) | Not stated on Laguna's page |
| Crystal Nebula | Coyote MBG164 | Cone 5 to 6, slow cool | Not recommended for foodware (Coyote) |
We found no glaze called Blue Nebula from AMACO or Mayco. The rest of this page covers Spectrum 863, the only glaze sold in the US under that exact name.
Spectrum 863 Blue Nebula at a glance
- Maker and code: Spectrum Glazes 863, listed as "863 NEBULA"
- Line: 850 series Raku Glazes (32 listings on Spectrum's site)
- Kiln: electric or gas raku kiln (Spectrum line text, as printed by dealers)
- Peak temperature: 1,600°F to 1,650°F (871°C to 899°C) for glazes 860 to 866, per dealer copies of Spectrum's instructions; see the conflict note below
- Application: set up for brushing; thin slightly for pouring or dipping
- Label: CL (caution label) on Spectrum's 2026 price list; lead free; over the copper threshold in liquid form
- Food use: not for dinnerware
- Sizes: 4 oz, pint, gallon
Pros
- Copper glaze that changes with reduction
- Sold in a 4 oz jar for testing
- Electric or gas raku
Cons
- Almost no maker description
- CL label, not for children
- 4 oz often out of stock at dealers
Who should skip it: anyone without access to a raku kiln, and anyone looking for a blue glaze for mugs or plates.
What Blue Nebula is meant to look like
Spectrum publishes Blue Nebula as a color chip, not in words; its raku color chart is an image, and its product page has no description tab. What Spectrum's line text does say is that raku colors depend heavily on reduction. Its dealers quote the example that "a glaze reduced in newspaper could be a beautiful blue color" while the same glaze reduced in sawdust could look metallic copper. Spectrum also notes that its charts are approximate because results vary with firing conditions.
Blue Nebula sits in the 860 to 866 group with 861 Metallic Flash, 862 Galaxy, 864 Sunspot, 865 Mars and 866 Deep Space. These are the copper-heavy glazes that Spectrum leaves off its list of non-toxic raku glazes. In practice, expect a blue to copper surface that changes from firing to firing, rather than one fixed color. Copper raku surfaces can also change color over months as they oxidize; our raku glazes guide explains why and what potters do about it.
Fire a few small test tiles with different combustibles (newspaper, sawdust, dry leaves) and different times before lid-off. Write each setting on the back of the tile so you can repeat the color you like.
How to apply Blue Nebula
Spectrum says its liquid raku glazes "are set up for brushing application". They can be poured or dipped, but should "probably be thinned with a little water" first. Spectrum's own pages give no coat count for 863. Potclays, Spectrum's UK distributor, describes Spectrum's raku brush-on glazes as having the consistency for brushing "where 2-3 coats are required", which is a sensible starting point for test tiles.
- Use bisqueware made from a clay that takes thermal shock; see our raku clay guide.
- Stir the jar well; copper glazes settle.
- Brush two to three even coats, letting each dry until the shine is gone.
- Keep the glaze off the foot and the area your tongs will grip.
- Let the piece dry fully before it goes in the raku kiln.
Firing Blue Nebula
Spectrum's raku instructions, as reproduced on Krueger Pottery and Sheffield Pottery listings, say its raku glazes "can be fired anywhere from 1600 F up to cone 06 (1850 F)" in an electric or gas kiln. They then give two peak bands: 850 to 856 and 868 to 879 to 1,700°F to 1,750°F (927°C to 954°C), and 860 to 866, which includes Blue Nebula, to 1,600°F to 1,650°F (871°C to 899°C). After the peak, the kiln cools to about 1,600°F (871°C) before pieces go into a lidded bin lined with combustible material for at least 20 minutes.
Source conflict: Clay-King's copy of the same Spectrum raku text says to "Fire to 1750 degrees F or 950 degrees C", with no separate band for 860 to 866. Spectrum's own product page prints no firing figure. Start at the lower 1,600°F to 1,650°F band for 863, look for a fully melted, glossy surface through the peep, and adjust with test tiles.
Our raku firing guide covers the whole process: loading, reading the melt, transfer and the reduction chamber. For the kiln itself, see raku kilns.
After the firing
Spectrum's dealer copy says to clean pieces after firing with water and a stiff brush, then rewarm them in the kiln to dry them, which it says helps set the colors. Let pieces cool fully before scrubbing; raku ware comes out of the bin very hot.
Safety and labels
Spectrum's 2026 price list marks 863 with an asterisk, which it defines as a CL caution label, and says glazes marked this way are "not for use with K-6 students". The line text explains why: eleven Spectrum raku glazes are lead free and non-toxic, while "the rest are lead-free, but are over the threshold limit for copper" and are not non-toxic in the liquid state. Read Spectrum's SDS before use, wear gloves, and keep the glaze away from food areas.
Raku is a fire hazard. Spectrum warns that red-hot pieces ignite the organic material in the bin, producing flames and smoke, and advises working outdoors with high-temperature gloves, eye protection, a respirator and a fire extinguisher. Gas raku kilns must be run to the kiln maker's instructions, local fire code and propane safety rules.
Is Blue Nebula food safe?
No. Spectrum's 2026 price list states that "the Raku firing process renders all glazes not safe for dinnerware use, regardless of composition." Raku clay stays porous and the copper glaze is not made for food contact, so use Blue Nebula on decorative pieces only. Our raku pottery guide covers what raku is good for.
Sizes, price and stock
Spectrum sells 863 in 4 oz jars, pints and gallons. On Spectrum's 2026 price list, the 4 oz jar sits in the single-digit dollar range, the pint around $20, and the gallon above $100; dealer prices were close to list in October 2026. Krueger Pottery and Sheffield Pottery both showed some sizes out of stock when we checked, so the 4 oz test size may need a back order. Check the live price before ordering.
What Blue Nebula does well
- Gives a copper raku surface whose color you can steer with the reduction material.
- Works in electric or gas raku kilns, per Spectrum.
- Comes in a 4 oz jar, enough for test tiles and a few pieces.
- Lead free, from a US maker with a full raku range to pair it with.
Weak points
- Spectrum publishes no written color description, coat count or firing figure on the product page.
- Dealer copies of Spectrum's firing text disagree on peak temperature.
- CL label: not for young students, and over the copper limit when liquid.
- Copper raku colors can shift over time.
- The name is easy to confuse with Laguna's cone 5 to 6 Nebula Blue.
Who should buy it, and who should skip it
Buy Blue Nebula if you already raku fire, or plan to, and want a copper glaze in a blue direction to experiment with. Skip it if you fire a regular electric kiln to cone 6, teach young children, or want predictable color from piece to piece.
Alternatives
- Spectrum 853 Cobalt Blue raku: a steadier blue for raku; see the comparison table in our raku glazes guide.
- Spectrum 862 Galaxy and 866 Deep Space: Blue Nebula's neighbors in the same 860 to 866 firing band, so they can share a load.
- For a blue with crystals at cone 6 in a normal kiln: Coyote Crystal Nebula, below, or AMACO Cosmos glazes.
Coyote Crystal Nebula (cone 6 alternative)
Crystal Nebula is picked as the cone 6 answer for potters who searched for a "nebula" glaze but fire an ordinary electric kiln. Coyote describes "a beautiful translucent glaze with pale blue tones and gold colored crystals", part of its Slow-Cool Crystal series. Coyote says these glazes should be slow cooled, run less than traditional crystal glazes, but still run.
- Code: MBG164
- Cone: 5 to 6 (Coyote's range), slow cool recommended
- Food use: "Not recommended for use on foodware"
- Sizes: pint, 1 and 3 gallon, 5 to 25 lb dry
Pros
- Fires in a normal cone 6 kiln
- Blue with gold crystals
- No drip tray needed per Coyote
Cons
- Needs a digital controller for slow cooling
- Still runs
- Not for food surfaces
Who should skip it: potters without a programmable controller, or anyone glazing mug interiors.
Sources: Spectrum Glazes product page for 863 Nebula, 850 series Raku Glazes category, Educational Resources page and 2026 Low Fire Glazes price list (USD); Spectrum raku listings at Krueger Pottery (863 Blue Nebula pint), Sheffield Pottery (850 series raku, 863 Blue Nebula) and Clay-King (865 Mars); Potclays Spectrum raku brush-on glaze listing; Laguna Clay MS-220 Nebula Blue product pages (liquid and dry); Art4fun and Glazeshare listings for Laguna MS-220; Coyote Clay & Color Crystal Nebula and Safety pages; Ahrefs SERP data for "blue nebula". Specs checked October 2026.