Starfish Reactive Tray
Oh, the joys of working with float glass! More and more glass artists are discovering the endless benefits and possibilities offered by using what is commonly-known as window glass for their creations. The difference between float glass and art glass hides within how the glass is made. Unlike art glass, float glass is made with a small amount of tin only on one side. This tin, combined with certain float frit colors, creates amazing reactions you will not find with art glass. Float glass also costs much less than art glass and is often even available free as scrap. There are so many different techniques that make working with float glass sheet and frit very rewarding.
The custom reactive technique presented in this
tutorial will help you create a fun and crowd-pleasing tray. Products from Glassycuts.com will make the process fun and easy.
Supplies used:
Window Float Glass, 8″ x 8″ (2)
Starfish
System 82 Float Glass Frit
Amber 0 Powder
Amber Size 4
Medium Size Giblets
Tools and Materials
Kiln Shelf Paper
Copper Mica Fine and Medium Enamel Sifters
UV-5F Lamp Tin Finder
Sharpie® Marker Pencil Writer
8‐1/2″ x 8‐1/2″ Square Slumping Mold
1. Gather all of your supplies, then clean both sides of the 8″ x 8″ float glass and the starfish shape. After you have cleaned the glass, you will need to find the tinned side of the float glass pieces. Only one side of the glass has the metal tin, and you cannot see it with the naked eye. Use the tin finder lamp and a Sharpie marker to find and mark the tin side of the glass, which is the one that glows from the ultraviolet light of the tin finder lamp. The side that does not have tin will not glow. Finding the tin side is significant, because we will be using both sides of the glass to create a reaction, a beautiful blue patina look that is unique to float glass.
2. Place one of the 8″ x 8″ sheets in the kiln on kiln shelf paper, tin side up. Start with the second 8″ x 8″ float glass sheet tin side up. Place the Glassy Cuts float glass starfish, tin side down, on top of the 8″ x 8″ sheet. Lightly trace the starfish onto the second piece of glass with a Sharpie. The marker will burn off in the kiln. Remove the starfish and set it to the side.
3. With a large sifter, lightly dust the Amber 0 powder all over the glass. Sift the powder so lightly that you can hardly see it. This will give a golden look to the tray. Too much and your tray will be less golden and more amber in color. With the medium size sifter, sift the Amber 0 powder a little heavier around the edges, undulating in and out to make the tray feel like the shoreline. Sift only enough powder for you to follow as a guideline.
4. Use the medium sifter to gently dump small mounds of Amber 0 powder around the edges of the glass. By dumping material into these areas, there will be high and low areas, with some thicker than others.
5. Fill in the starfish with taller and heavier mounds of the Amber 0 powder. These mounds will be part of creating the reaction we are looking for.
Note: To avoid wasting product, clean your workspace of the excess Amber powder and place it back into the jar. Make sure not to add fingerprints to the project while moving it.
6. With your fingers, sprinkle Amber size 4 frit around the edge of the glass on top of the powder mounds. Add the frit to the starfish as well. Some frit may sprinkle onto the middle of the glass. That is okay, but don’t let too much get loose or your piece or it may be more spotted than you like. Note: If too much sprinkles out, use tweezers or lightly wet your finger to pick up the excess. The wet finger trick also works if the powder spills onto an area where you would not prefer the frit to be.
7. With a pencil writer, apply copper mica in swirl patterns on the starfish and all around the edge of the tray.
8. Add the starfish shape and decorate the piece with the giblets. Place the Glassy Cuts starfish, tin side down, on top of the powder mounds and sprinkle the medium size Glassy Cuts giblets around the edge of the tray on top of the mounds. You can also create your own frit by crushing scrap float glass and sifting out the smaller pieces.
Note: Giblets are made from ground up float glass. Because the float glass has tin on one side, the giblets also have tin on one side. It’s a toss-up on which side of the the giblets will fall onto the powder. The side with the tin will have a reaction, and the side without will not. I chose to be surprised! The reaction happens because the amber frit is sandwiched between two pieces of glass where one is tin side up and one is tin side down. Also note that when sprinkling the giblets around the edge, you want to have big enough pieces that will show the reaction, but don’t let them hang over the edge.
9. This photo shows the piece after the first firing. You could stop there, but if you prefer, continue with a second slump firing using the 8″ x 8″ square slumping mold to finish the tray. Here are the suggested full fire and slumping schedules. Remember, though, that each kiln fires differently, so you may need to adjust the schedule for your kiln.
Float Glass Firing Schedule
Segment 1: Ramp 600°F/hr to 1510°F and hold 10 min. Segment 2: Ramp 9999 (AFAP*) to 1050°F and hold 30 min. Segment 3: Ramp 100°F/hr to 850°F and hold 15 min. Segment 4: Ramp 9999 (AFAP*) to 100°F and end.
*as fast as possible
Slumping Schedule
Segment 1: Ramp 300°F/hr to 1300°F and hold 10 min.
Segment 2: Ramp 9999 (AFAP*) to 1050°F and hold 45 min.
Segment 3: Ramp 75°F/hr to 850°F and hold 20 min.
Segment 4: Ramp 9999 (AFAP*) to 100°F and end.
*as fast as possible
Give us a call if you have any questions!
Frequently asked questions
Full Fuse Normal Small Project
- *600 – 1510- 10
- Full – 1050 – 10*
- Full*a – 850 – 10*b
- 100 – 100 – OFF
- *If you have a thick or multi-layer project, you will want to slow this down from 600 to 300, then up to 1500.
- *If you have a large, thick, or multi-layer project you will want to hold your project longer. I hold my trays for 45 minutes to 1 hour..
- a*Again, depending upon thickness or layering, you will want to slow the process down from a full drop in temperature to anywhere from 50-85 degrees per hour to 850.
- b* Again, hold longer for more complicated, thicker projects.
NOTE: Kilns ramp & hold their heat differently. Practice with your kiln! Some may require you to come up or down in temp at a different rate.
Float Glass Mosaic
Full Fuse Mosaic Sheet- 1 Layer 600- 1510- 10 Full- 1050 – 10 * Full- 850 – 10 * ** 100- 100 – off Full Fuse Mosaic On Cut Outs (Glassy Cut Shapes) 600- 1510- 10 Full- 1050- 10* Full- 850- 10* ** 100 – 100 – off *hold longer for thicker projects ** come down slower for thicker projects Slump Mosaic Pieces 300 – 1300 – 10 Full- 1050 – 30*a Full- 850- 20*b&c 100- 100- off *a- 30 minutes or longer depending on the size & thickness of the mold you’re using. Mosaic pieces that are stacked 3 or more in height should be slumped very slowly or your project will split. *b- Slower than the full 9999 depending on the size & thickness. We will slow this down as love as 50 degrees per hour *c- Hold here longer also if it’s a thicker piece or on a metal mold. NOTE: Metal molds hold their temp longer than glass so you could shock you glass and break it.
Tack Fuse
- *600 – 1425 – 11
- Full – 1050 – 10*
- *Full – 850 – 10
Same info as above for ramping up or annealing down. Temps change with the size, thickness, and multi-layers of your project. Multi-layers include mosaic too.
Slump/Drape Temps
- *300 – 1300 – 10
- *Full – 1050 – 10
- *Full – 850 – 10
- 100 – 100 – OFF
Again, be careful with ramping your temp too high in the start or dropping your temps too fast. If you are slumping on or over metal- slow it way down to avoid thermal shock from metal retaining its heat longer than glass. NOTE: Metal molds hold their temp longer than glass which can shock your glass and break it.
Fire Polish
Slow – 1300 – 5 Ramp down slowly *Remember- any texture or embossing will flatten out at 1300. A trade trick is to grind your piece & add a swab of Liquid Luster from Olympic Glass in Seattle.
Steam Cast-A-Lot Casts
Do not steam plaster of paris molds. Both types of molds will need kiln-wash prior to casting glass!
- 9999 – 190 – 3 hrs
- 250 – 1500 – off
*Will throw a good amount of steam so your kiln should have stainless steel parts/ hangers or it will rust!
Fusing & Slumping Bottles
SMALL BOTTLES:
300 – 1100 – 5
300 – 1300 – 10
500 – 1425 – 5
9999 – 1000 – 30
100 – 200 – off
*LARGE BOTTLES:
300 – 1100 – 30
300 – 1300 – 60
500 – 1425 – 5
9999 – 1000 – 60
50 – 800 – 60
100 – 200 – off
*Large bottles should have temps that are held out longer to avoid thermal shock. This is due to the base laying down & creating a thick area compared to the rest of the bottle.
Bubble Squeeze
Ramp up at a normal rate for project to 1300 – Hold for atleast 15 minutes (test) Then ramp up normally to fusing temp.
Tempered Glass
In a mold: 1. 500 – (1425 to 1450) – 10 2. Full – 1050 – 10* 3. 200 – 100 – off Out of the mold: use regular tack or full fuse, depending on the final desired look
Float Glass Color Cheat Sheet
A simple guide to choosing, layering, and combining float glass colors
First things first: our colors don’t behave like paint
Float glass colors don’t mix the way a traditional color wheel does. When colors overlap, they layer — they don’t blend. That means:
- Red + blue ≠ purple
- Blue + yellow ≠ green
- Mixing across color families often creates muddy browns or grays
This isn’t a mistake — it’s just how glass works.
Color “Houses” (Your safest starting point)
When choosing colors, we recommend staying within one color family. Cool Colors (work beautifully together)
- Blues
- Greens
- Purples
- Pinks
Warm Colors (work beautifully together)
- Reds
- Oranges
- Yellows
Neutrals (their own special category)
- Whites
- Blacks
- Grays
Neutrals pair best with other neutrals and cool colors, but they don’t always play nicely with warm colors. If you choose to mix across color houses — go for it! Just know that results may be unpredictable (and sometimes surprisingly cool).
Layering Rule: Light → Dark
When layering glass powders or frit, order matters. Unlike paint, glass doesn’t mix together; it stacks. Because of this, the sequence in which you apply color has a major impact on the final result. The golden rule is simple: Start with your lightest color and build up to your darkest. This matters because dark glass is extremely strong. If a dark color is placed underneath a lighter one, it can visually overpower it, causing the lighter color to disappear or become muddy. This often feels surprising to beginners, but it’s simply how light behaves in glass. When light or transparent colors are placed first, they can still glow through darker layers added on top. This allows color relationships to stay visible and intentional. In practice, this usually means beginning with light, transparent colors, adding medium tones next, and saving darker or more saturated colors for last. This approach gives each layer a chance to be seen rather than absorbed. If you reverse this order, lighter colors may seem to vanish entirely because the darker glass beneath is blocking light from reaching them.
Combining Transparent and Opaque Colors
When working with both transparent and opaque colors, layering becomes even more important. Transparent colors allow light to pass through, while opaque colors block it. Because of this, transparent colors should generally be applied first, with opaque colors layered on top. In most cases, opaque colors work best as the final layer. This creates clear visual separation between colors, adds contrast, and allows transparent layers beneath to contribute depth without being lost.
Opaque vs. Transparent
How light affects your colors
One of the most important things to understand about float glass is how it interacts with light. Color in glass isn’t just about hue — it’s about whether light can pass through the material or not.
This is where transparent and opaque colors behave very differently.
Transparent Colors
Transparent glass allows light to pass through it. When layered, transparent colors don’t cover what’s underneath — they build on it.
This means:
- Underlying layers remain visible
- Colors stack and interact visually
- Pieces feel lighter, deeper, and more dimensional
Transparent colors are great for glowing effects, subtle gradients, and layered designs where you want depth.
Think of transparent glass like layers of colored light.
Opaque Colors
Opaque glass blocks light. Once an opaque color is applied, it becomes the visual stopping point — whatever is underneath it is largely hidden.
This means:
- Colors appear bold and solid
- Underlying layers may disappear
- Opaque colors visually sit “on top”
Opaque colors are powerful and beautiful, but they are dominant — even a small amount can overpower lighter or transparent layers.
Download Your Free Firing Schedule
Your quick-start guide to working with System 82 Float Glass.