Updated Blue Bend instructions:
Blue Bend is a specialized water soluble, non toxic, sugar-based filler used to support thin-wall brass tubing during bending. The following are some guidelines for using Blue Bend successfully in your projects. If you need additional help, please reach out! As you’re probably aware, tube bending can sometimes feel more like black magic than science, but I’ll do my best to share my experiences and help you to achieve your goals.
Materials & Equipment
Blue Bend
Brass tubing, clean and dry
Heat source – microwave, induction plate, hot plate, or controlled burner.
Thermometer – accurate to 1°F in the 250–400°F range
Heat-resistant pouring container (borosilicate glass, metal or heavy-duty silicone)
Insulated gloves and safety gear:
Heat-resistant gloves
Eye protection
Apron or long sleeves
Clamps, bending form, or mandrel for shaping
Large soft flame torch or other heat source for removal
Bucket of water to remove any residue.
Safety Notes
Read all instructions before using Blue Bend.
Always wear heat-resistant gloves and eye protection when handling melted Blue Bend.
Keep the work area free of moisture to avoid dangerous steam eruptions when pouring.
Maintain good ventilation when heating, especially at higher temperatures.
Do not leave heated Blue Bend unattended.
Heating Instructions
Setup
Make sure tube is clean and completely dry. Any water will cause steam to shoot molten Blue Bend from the tube. I like to pickle my tubes before bending to remove any scale or oxides that may interfere with the Blue Bend adhering to the wall.
Plug one side of the tube with a rubber stopper, or tape the open end closed with some tape and secure the tube upright for pouring.
(Optional) Preheat the tubing slightly (150–200°F) to reduce thermal shock and improve flow. ** I don’t personally do this but I’ve heard that some do, especially when filling small diameter or long tubes.
Method 1: Melt Blue Bend (microwave)
Place Blue Bend pieces in a Pyrex or or borosilicate glass container, preferably one with a pouring spout and handle. (Optional: spritz a small amount of water into the glass- see notes below)
Use 50% power at 5 minute increments until the Blue Bend starts to liquify.
Heat gradually to 290–310°F, reducing the time increments as you approach the target and watching closely for any foaming or boiling over. Stir gently throughout for even heating and to allow trapped moisture to escape. My preferred stirrer is a glass lab stirring stick.**
Do NOT exceed 340°F, as this can scorch the mixture or alter its properties.
Stir occasionally for even heating and to release trapped air bubbles.
Readiness Check
The mixture should be fully liquid, with a smooth, syrup-like consistency.
Avoid pouring if there are visible crystals or chunks remaining.
NOTE** Never let Blue Bend cool in a glass container. If you do, and you put it back into the microwave, it will shatter the container when it heats and expands. If you ever accidentally leave Blue Bend in a glass container, heat the plug up with a flame until you can slide the plug out, break it apart and melt again.
Method 2: Melt Blue Bend (induction)
NOTE: Induction or hot plate heating carries a higher risk of scorching than the microwave. It is more effective for larger batches
Cover the bottom of a heavy bottomed pot with 1/8 inch of water, and place the Blue Bend blocks or shards on top. The water will help prevent scorching as the Blue Bend begins to melt.
Heat Blue Bend in an even, controlled manner, stirring regularly and watching for the water to boil away. The Blue Bend will boil violently at 220-270°F and then will start to calm as all the water is driven off.
Heat to 290-310°F, stirring to keep the heat even and allow trapped moisture to release.
Readiness Check
The mixture should be fully liquid with a smooth, syrup-like consistency.
Avoid pouring if there are visible crystals or chunks remaining, or if the Blue Bend is still actively boiling.
Pouring & Cooling
Pour Carefully
Pour the Blue Bend into the tubing slowly and steadily, avoiding splashing.
Fill completely to eliminate voids, tapping the tube lightly to help bubbles rise.
Cool Until Solid
Allow the filled tube to cool at room temperature or with gentle airflow.
Do not shock cool with cold water — this can cause cracks in the filler.
Check for Readiness
Once fully cooled, Blue Bend should feel hard and glass-like when tapped. There should be no heat detectable in the tube. I often use an Instant Read thermometer to confirm that the tube is at room temperature.
Bending the Tube
Mount the tubing in your bending form or mandrel setup.
Bend slowly and evenly, maintaining consistent pressure throughout.
Removing Blue Bend
Use a large, soft flame to warm the tubing gradually until Blue Bend begins to melt. Blue Bend absorbs a lot of heat, so pause regularly to let the heat dissipate towards the center of the Blue Bend plug.
Drain out into a heat-safe container for reuse. I’m fond of a large, thick, silicone bucket often sold as a concrete or thinset bucket liner.
Soak the empty tube in water to remove residue.
Some disorganized thoughts that you might benefit from knowing:
Blue Bend is sensitive to moisture. If it’s too wet, you may notice issues with roundness. If too dry, it is brittle and you may notice deeper segments in the outer wall of the tube. If you heat to a consistent temperature range (290-310°F) and make sure that the Blue Bend finishes boiling off the moisture and the surface calms, you should always be bending in the sweet spot (pun intended, you know because of the sugar).
It’s a good idea to store Blue Bend in some sort of sealed container or it will normalize its hydration with the air. When Blue Bend absorbs a lot of ambient moisture, it sometimes will foam up in the microwave and spill over the wall of your container. That's one good reason to keep an eye on things as the temperature increases. Foaming is not bad as long as the surface is calm and you’ve reached the 290-310°F range when you’re ready to pour. That means that the right amount of water has boiled off and you should be ok to pour and bend.
Blue Bend is not intended to prevent all segmentation on the outside of the bend. When researching bending and developing Blue Bend, it became clear that when dealing with roundness, inside buckling, and outside stretching, it was only possible to optimize 2 of them. I chose to optimize for good roundness and no buckling because in my work, roundness is important to preserve for acoustics purposes, and the finishing processes for addressing inside tube buckling and wrinkling almost never preserves the tube roundness or the geometry. Using a flat burnisher on any outside segments or stretch marks blends them in nicely and does not change the dimensions or roundness tolerances of parts I’m working with.
You can make Blue Bend more elastic by adding some water and heating to a lower temperature (280°F or so). This allows the Blue Bend to hold onto slightly more moisture and thus it will act a little bit softer. I don’t recommend doing this unless you’re using large diameter tube, but you can adjust some variables and experiment with optimizing the characteristics to suit your project. On the flip side, if you find Blue Bend to be too soft, especially after multiple cycles, you can heat it a little hotter to drive off more moisture (320-330°F).
Blue Bend is theoretically infinitely reusable, but it cannot be restored once it has been overheated. The blue will turn to green and you will notice wildly different bending characteristics. You can safely dispose of it in the trash.
I sometimes use a Shore D hardness tester to check my Blue Bend. My habit is to pour my tube and then to pour any leftovers into a small silicone muffin liner. I check the muffin plug with a Shore D tester and am expecting to see something between 70 and 80. If I see something less than 50 or something where the needle seems to continue to dive, I know that either the plug is too wet, or it needs more time to set up.
Good luck, happy bending, and please reach out if you need any help!