Mustafa Umut Sarac Posted February 27 Report Posted February 27 Hello there, which chemicals contributes to these red , purple , blue , golden or bronze colored zones on tamahagane jewel steel ? Thank you Umut Quote
Bazza Posted February 27 Report Posted February 27 I've always taken them to be oxides of iron ('termpering colours') without knowing or understanding if they have a chemical formula!! BaZZa. Quote
Mustafa Umut Sarac Posted February 27 Author Report Posted February 27 Just now, Bazza said: I've always taken them to be oxides of iron ('termpering colours') without knowing or understanding if they have a chemical formula!! BaZZa. Hello Bazza, Chatgpt had a answer to my question, The colors observed on Tamahagane jewel steel—red, bronze, blue, and purple—are primarily due to oxide layer formation and light interference effects on the steel's surface. Different elements in the steel contribute to the oxidation process, leading to distinct hues. Here’s a breakdown of which chemicals or compounds are responsible for these colors: 1. Red & Bronze Zones Iron oxides (Fe₂O₃, Fe₃O₄) When steel is heated, iron reacts with oxygen to form iron(III) oxide (Fe₂O₃), which gives a reddish hue. A thinner oxide layer may appear bronze or golden due to interference effects. Copper (if present as an alloy element) Some jewel steels may have trace amounts of copper, which can contribute to a reddish or bronze tint when oxidized. 2. Blue & Purple Zones Iron oxides (Fe₃O₄) & Magnetite layers Fe₃O₄ (magnetite) produces blue-black hues. Interference effects from very thin FeO layers can also lead to a blue or purple sheen. Titanium & Chromium Oxides (if present in alloy) Titanium oxides (TiO₂) & Chromium oxides (Cr₂O₃) can also create blue to purple hues. Heat Tinting & Light Interference Different oxidation thicknesses create thin-film interference, resulting in blue, purple, and other iridescent colors. Color Development Sequence with Heat When steel is heated, the oxide layer grows thicker, creating different colors: Pale yellow → Bronze (thin Fe₂O₃ layer) Reddish → Brown (thicker Fe₂O₃) Purple → Blue (Fe₃O₄ and interference effects) Dark blue to black (thick oxide layers, magnetite formation) Quote
Bazza Posted February 27 Report Posted February 27 Stupendous. Thank you Mustafa. Question resolved. Quote
Brian Posted February 27 Report Posted February 27 If you're into the researching aspect of these steels (Japanese swords) then here are a few links to check out. There are many more online. https://mrforum.com/...9781945291173/75.pdf https://www.esomat.o...esomat2009_07018.pdf https://pdf.sciencedirectassets.com https://www.hilarisp...169-0022-1000162.pdf https://www.cambridg...a-japanese-sword.pdf https://www.pyrometa...ags2000/pdfs/133.pdf https://www.matec-co...esomat2015_07001.pdf https://www.jstage.j...erseas/1/2/1_49/_pdf https://www.researchgate.net/profile/Anh-Pham-119/publication/338464901_Crystallographic_Structure_Study_of_a_Japanese_Sword_Masamitsu_made_in_the_1969_using_Pulsed_Neutron_Imaging/links/5e1680ef92851c8364bd39d7/Crystallographic-Structure-Study-of-a-Japanese-Sword-Masamitsu-made-in-the-1969-using-Pulsed-Neutron-Imaging.pdf https://papers.ssrn....?abstract_id=4692889 http://www.nihontome...e_and_technology.pdf https://www.jstage.j...mon/25/3/25_206/_pdf http://naippe.fm.usp...by/Sawasu_Part_2.pdf Only linking to them, nothing hosted here in case of any copyright issues. 2 Quote
Mustafa Umut Sarac Posted February 27 Author Report Posted February 27 9 hours ago, Bazza said: Stupendous. Thank you Mustafa. Question resolved. Barry , there are lot more to say, When steel is heated, iron reacts with oxygen to form iron(III) oxide (Fe₂O₃), which gives a reddish hue. which celcius degrees between ? ChatGPT: Iron(III) oxide (Fe₂O₃), which gives a reddish hue, forms on steel when heated in air. The temperature range for Fe₂O₃ formation depends on oxidation conditions, but generally: Temperature Range for Fe₂O₃ (Red Iron Oxide) Formation: 200°C to 500°C → Fe₂O₃ begins forming as a thin reddish layer. 500°C to 800°C → Fe₂O₃ thickens, becoming more visible. Above 800°C → Fe₂O₃ can convert into Fe₃O₄ (magnetite), which is black or blue-black. At lower temperatures (~200–300°C), Fe₂O₃ appears as a thin light red or orange-brown layer. As temperature increases, the layer thickens and darkens. If heating continues above 800°C, Fe₂O₃ transitions to Fe₃O₄, losing its red color. Would you like to control the oxidation to achieve a specific color on your Tamahagane steel? others ? Besides iron oxides (Fe₂O₃, Fe₃O₄), other chemicals and trace elements can contribute to the red, bronze, blue, and purple zones on Tamahagane jewel steel—especially if the steel contains natural impurities from the traditional smelting process. Here's a more detailed list of which chemicals contribute to each color: 🔥 Red & Bronze Zones (200°C – 500°C) Chemical Color Temperature (°C) Notes Iron(III) Oxide (Fe₂O₃) Reddish 200–500°C Main red pigment on steel surfaces. First oxide layer. Copper Oxide (Cu₂O) Reddish-brown 200–400°C If small traces of copper impurities are present in Tamahagane ore. Chromium Oxide (Cr₂O₃) Bronze-green 300–500°C If the steel contains chromium from impurities in the iron sand. Nickel Oxide (NiO) Yellow-Bronze 300–450°C Rare in Tamahagane, but could appear if nickel is present. 🌊 Blue & Purple Zones (300°C – 600°C) Chemical Color Temperature (°C) Notes Iron(II,III) Oxide (Fe₃O₄) Blue-Black 300–600°C Second oxide layer. Blue tint at thinner layers. Titanium Oxide (TiO₂) Blue or Purple 350–550°C From natural titanium impurities in Japanese iron sand (Satetsu). Chromium Oxide (Cr₂O₃) Greenish-Blue 400–600°C Only if chromium is present. Manganese Oxide (Mn₂O₃) Purple-Blue 400–550°C Common in high-quality Tamahagane from Satetsu. 🔥 Purple Zones (450°C – 600°C) Chemical Color Temperature (°C) Notes Titanium Oxide (TiO₂) Violet 400–550°C Natural impurity from Satetsu. Manganese Oxide (Mn₂O₃) Purple-Blue 450–550°C Rare but can create purple halos around blue areas. Iron Oxide Interference Layers (FeO) Purple 500–600°C Due to thin-film interference from multi-layered oxides. How Do These Colors Appear in Tamahagane? The traditional folding process of Tamahagane refines the steel but leaves micro impurities like titanium, manganese, and copper inside the metal. When polished and heated, different oxide layers grow on the steel at different rates. This creates the rainbow-like "jewel steel" effect—especially on high-quality Tamahagane. 🔑 Layer Structure Explanation Layer Color Thickness (nm) Metal Oxide Top Layer Blue, Purple 100–300 nm Fe₃O₄ + TiO₂ + Mn₂O₃ Middle Bronze 300–500 nm Fe₂O₃ + Cu₂O Base Red 500–700 nm Fe₂O₃ Summary Color Ranges: Color Chemicals Temperature (°C) Red Fe₂O₃, Cu₂O 200–500°C Bronze Fe₂O₃, NiO, Cr₂O₃ 300–500°C Blue Fe₃O₄, TiO₂, Cr₂O₃ 350–600°C Purple TiO₂, Mn₂O₃, Fe₃O₄ 450–600°C 🔥 How to Control These Colors on Tamahagane: Color Temperature Time Atmosphere Red 200–300°C Short Dry air (Oxygen-rich) Bronze 300–450°C Medium Dry air Blue 350–550°C Long Dry air or slightly humid Purple 450–600°C Long Dry air + small humidity Conclusion The "jewel steel" effect of Tamahagane is a combination of: Traditional smelting impurities Controlled oxidation layers Natural elements in Satetsu (iron sand) If you want to enhance red, blue, or purple zones, the best method is: Polishing with charcoal or whetstones. Heat tempering between 200–600°C. Using different atmospheres (dry air vs. humid air). 1 Quote
Mustafa Umut Sarac Posted February 27 Author Report Posted February 27 Here’s a step-by-step guide to achieving all major colors on your Tamahagane jewel steel, using precise temperature control and oxidation methods. 1. Surface Preparation (Before Heating) Before applying heat, prepare the steel for uniform oxidation: ✅ Polish to a mirror finish → Use 800–2000 grit sandpaper or a buffing wheel. ✅ Clean with acetone or alcohol → Removes oil and fingerprints. ✅ Degrease completely → Any residue can create uneven colors. 2. Heating & Color Formation Table Each color appears at a specific temperature range, controlled by either torch heating or an oven. Color Temperature (°C) Oxide Formed Key Techniques Light Bronze / Gold 200 – 250 Fe₂O₃ (thin layer) Light heating, even flame Deep Bronze 250 – 300 Fe₂O₃ (thicker) Hold temp for a few minutes Purple 300 – 400 Fe₃O₄ + SiO₂ (thin) Even heating, slow cooling Deep Blue 400 – 500 Fe₃O₄ + Cr₂O₃ (if present) Hold at temp for better depth Dark Blue / Black 500 – 800 Thick Fe₃O₄, FeO High temp, low oxygen Red / Orange 250 – 450 Fe₂O₃ (increasing thickness) Expose to more oxygen Greenish Tint 400 – 700 Cr₂O₃ or Fe-P compounds Requires chromium in alloy 3. Methods for Each Color A) Light Bronze / Gold (200–250°C) Heat gently with a torch or in an oven at 200–250°C. Keep exposure brief to avoid going into deeper bronze. Best cooling method: Air cooling. B) Deep Bronze (250–300°C) Hold the steel at this temp longer (1–2 minutes). If using a torch, pass the flame evenly until the color develops. Best cooling method: Slow air cooling. C) Purple (300–400°C) Slowly increase heat; the steel will first turn bronze, then purple. Use an oven for even color distribution. Best cooling method: Air cooling (not quenching). D) Deep Blue (400–500°C) Even, sustained heating is required. A propane torch or an oven works best. Reduce oxygen exposure slightly for a deeper blue. Best cooling method: Slow air cooling. E) Dark Blue / Black (500–800°C) Let Fe₃O₄ grow thicker by holding at high temperatures. Low oxygen will darken the color. Best cooling method: Slow air cooling. F) Red / Orange (250–450°C) Expose to more oxygen by heating in an open flame. Increase oxidation duration to thicken the Fe₂O₃ layer. Best cooling method: Air cooling. G) Greenish Tint (400–700°C, with Chromium) This is rare in pure Tamahagane, but if there’s chromium or phosphorus, heat to 400–700°C. Heat slowly and oxidize gently. Best cooling method: Slow air cooling. 4. Best Heating Techniques Option 1: Torch Heating (Best for Small Pieces) Use a butane, propane, or oxy-acetylene torch. Move the flame evenly across the steel. Stop heating immediately when the desired color appears. Quench or air cool depending on the desired result. Option 2: Oven Heating (For Uniform Color) Preheat an oven or kiln to the exact temperature. Place the steel inside and monitor color changes. Remove and air cool when the target color is reached. Option 3: Controlled Atmosphere (For Professional Results) A salt bath or reducing atmosphere kiln ensures perfect oxidation control. Best for consistent blues, purples, and blacks. 5. Locking in the Colors (Sealing & Finishing) Once the desired color is achieved, seal it for durability: ✅ Clear lacquer → Jewelry & display pieces ✅ Renaissance wax → Protects while keeping a natural look ✅ Automotive clear coat → Best for long-term durability Final Tips ✅ Heat slowly for better control. ✅ Monitor oxidation changes carefully—colors appear in order. ✅ Polish & clean before heating for an even surface. ✅ Test on a scrap piece first! 2 Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.