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Posted: 11/30/2025 3:52:31 AM EDT
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I have some old Birchwood Casey from my dad that's probably from last quarter of 20th century. I noticed that it seems to work much better and faster than the 21st century stuff. The old can says it's Selenium Dioxide The newer cans say it's a compound of Selenious Acid and Fluoboric Acid Have you all seen this (if you've been using it long enough to have used the old 20th century compound)? ChatGPT confirmed the newer composition is known to not work as well what is the difference between selenium dioxide and a compound of selenious acid and fluoboric acid? **Short answer:** *Selenium dioxide (SeO )* is a single, simple inorganic compound. A *compound of selenious acid and fluoboric acid* is a **salt** formed by reacting **selenious acid (H SeO )** with **fluoboric acid (HBF )**, yielding something like **selenium(IV) fluoborate**, e.g. *SeO(BF ) * or related ionic species. These are chemically very different materials. --- ## **Detailed explanation** ### **1. Selenium dioxide (SeO )** * **Chemical formula:** SeO * **Oxidation state of Se:** +4 * **Structure:** * Solid: polymeric chains * Gas: O=Se=O (linear molecule) * **Properties:** * White to pale-yellow solid * Sublimes easily * Widely used as an oxidizing agent in organic chemistry * Dissolves in water to form **selenious acid (H SeO )** So SeO is essentially the **anhydride** of selenious acid. --- ### **2. Compound of selenious acid + fluoboric acid** If you mix **selenious acid (H SeO )** with **fluoboric acid (HBF )**, you do **not** get selenium dioxide. Instead, you typically form a **selenium(IV) fluoborate salt**, for example: * **SeO(BF ) ** * Or hydrated ionic complexes like **[Se(OH) ] ** with **BF ** counterions **Key differences:** * Contains **BF (tetrafluoroborate)**, a non-coordinating anion * Usually forms **ionic** compounds, not covalent molecules like SeO * Much more stable in aqueous solution than SeO * Properties differ completely (solubility, reactivity, stability) Essentially, you are forming a **salt of Se(IV)** rather than an oxide. --- ## **3. Summary of the difference** | Property | Selenium dioxide (SeO ) | Product of H SeO + HBF | | ----------------- | ----------------------------- | ----------------------------- | | Chemical type | Covalent oxide | Ionic fluoborate salt | | Contains BF ? | No | Yes | | Relationship | Forms selenious acid in water | Derived *from* selenious acid | | Oxidizing ability | Strong | Often weaker or different | | Physical form | Solid oxide | Salt, often hydrated | application is for blackening aluminum. Is one more controlled or restricted by the government or more costly than the other? For **blackening aluminum**, the difference between using **selenium dioxide (SeO )** vs. a **selenious-acid/fluoboric-acid compound** mainly shows up in **regulatory status, availability, cost, and handling requirements**. Here's the practical, real-world comparison: --- # **1. Regulatory & Government Control** ### **Selenium dioxide (SeO )** * **Regulated as a hazardous substance**, but **not specifically controlled** by DEA, ATF, or other special agencies. * Listed by OSHA and EPA as a **toxic selenium compound** requiring standard handling (gloves, ventilation, proper waste disposal). * Typically ships as a **hazardous material** (UN 3283, Class 6.1 toxic). * No special licenses required, but suppliers may require: * Employer/industrial account * Hazmat agreement ### **Selenious acid (H SeO )** * More tightly regulated because it is: * Highly toxic * A strong oxidizer * Usually sold as a **liquid**, which raises shipping/transport restrictions * Some vendors require a **business/industrial verification** to sell it. * Still **not a controlled substance**, but somewhat harder for consumers to purchase. ### **Fluoboric acid (HBF ) or tetrafluoroborate salts** * **Corrosive, but not especially regulated** beyond hazmat rules. * BF salts are easy to ship compared to strong acids. ### **Combined selenious acid + fluoboric acid (selenium(IV) tetrafluoroborate mixtures)** These mixtures: * Are sold specifically for **aluminum blackening baths** * Are typically easier to purchase because they're not viewed as "laboratory reagents" * Slip through some supplier restrictions because: * It's a **formulated product**, not a pure toxic chemical * It's packaged for industrial finishing, not reactive lab chemistry **In practice:** It is usually **easier to buy commercial blackening chemicals (selenium + fluoborate mixtures)** than to buy pure selenium dioxide or pure selenious acid. --- # **2. Cost** ### **Selenium dioxide** * Relatively expensive because it's a purified reagent. * Typically $80 $150/lb for industrial quantities. ### **Selenious acid** * Costs similarly high or higher. * Liquid shipping adds cost. ### **Fluoboric acid** * Very cheap (common plating acid). ### **Commercial selenium-based blackening solutions** Usually sold as: * "Aluminum blackener concentrate" * "selenium and fluoride based surface treatment" These are typically: **Cheaper** than buying SeO **Easier to use** **More stable in solution** **Lower shipping cost** than pure SeO or H SeO **Easier legally**, because they're sold as "metal finishing chemicals" --- # **3. Use in Aluminum Blackening** Selenium dioxide is *not* normally used directly. Instead, **selenium compounds in acidic fluoride solution** form a controlled, even black finish. The fluoboric system has advantages: * More uniform black * Less aggressive attack * More stable bath chemistry * More forgiving concentration window * Longer bath life It's the industry standard. --- # **Bottom Line** ### **Which is more restricted?** * **Selenious acid and selenium dioxide are more restricted** because they are pure toxic chemicals. * **The commercial selenium-fluoborate blackening solutions are less restricted** because they are productized and diluted. ### **Which is cheaper?** * **Commercial selenium fluoboric blackening formulas are cheaper overall** than buying SeO and making your own bath from scratch. ### **Which should you use for blackening aluminum?** * Use the **selenium + fluoboric acid commercial blackener**. * Much easier to buy, safer to ship, and gives a better finish. Birchwood Casey Aluminum Black used to contain selenium dioxide and now it says selenious acid and fluoboric acid. The older version seems to work much better. You're not alone many people who used [Birchwood Casey Aluminum Black](https://ads.midwayusa.com/product/1006362177?pid=707229&utm_source=chatgpt.com) report very different results now that the formula has apparently changed (from a selenium-dioxide based chemistry to a selenious-acid / fluoboric-acid / sulfate/acid mixture). There are a few reasonable explanations why the "old version" might have *worked better* and why users now often find it less effective. --- ## What changed and how that impacts performance * The current MSDS for Aluminum Black lists **selenious acid, phosphoric acid, fluoboric acid, cupric sulfate, nickel sulfate** (and water) as ingredients. ([Noorda Manufacturing][1]) * Circumstances on forums reflect widely varying success depending strongly on alloy type, how freshly exposed the bare aluminum is, and how strictly prep instructions are followed. ([AR15][2]) * In older discussions about blackening/blueing processes with selenium-dioxide or selenium-containing baths, there's a hint that simpler formulations (with fewer interfering salts) can produce more consistent, deeper color whereas baths with multiple metals or acids need tighter control and may "burn out" or deposit uneven coatings over time. ([Free Patents Online][3]) In other words: the newer Aluminum Black mixes more chemicals (fluoborates, phosphates, copper/nickel sulfates) all of which may interfere with a clean, uniform "selenium-driven" reaction on the aluminum surface. If anything is off (alloy makeup, oxidation, surface prep, concentration, timing), you get patchy, weak "black" instead of a deep, even finish. That matches many user complaints. --- ## What this means in practice and why the old version *felt* better * **Less consistent results now.** On forums users say that with older versions they got nice dark patches quickly after a few coats; newer versions often result in "not black maybe dark gray," or no darkening at all. ([AR15][2]) * **Very sensitive to prep and aluminum alloy.** Some alloys respond poorly; even on "soft" or freshly exposed aluminum, success seems hit-or-miss with the current formula. ([AR15][2]) * **Corrosive and unstable.** The MSDS warns the mixture is "poisonous, corrosive, causes severe burns to skin/eyes" and strongly suggests careful handling. ([Noorda Manufacturing][1]) * **By design, it may have been "watered down."** To meet safety or environmental regulations, manufacturers may have diluted or reformulated the active selenium chemistry sacrificing "blackening performance" for easier disposal, safer shipping, or lower liability. Indeed, earlier patents and literature about selenium-based blackening baths note issues with toxic byproducts and disposal. ([Free Patents Online][4]) So yes it's quite plausible (and consistent with many user reports) that the "old formula" with more straightforward selenium chemistry gave a more robust, deeper, more reliable black finish than the current, more complex/"managed" mixture. --- ## What you might do about it or check if you want old-like performance * **Thorough cleaning and bare-metal prep.** Remove all oils, coatings, anodizing, oxidation ideally down to bright bare aluminum. Any residue will strongly inhibit the chemical reaction. * **Test on scrap first.** Because response varies by alloy and surface condition, test on a small piece of same alloy rather than the actual part. * **Consider alternate finishing options.** If uniformity / durability matters (not just quick touch-up), you might consider **anodizing** or other modern blackening/coating methods rather than chemical "cold blackening." In fact, many sources recommend re-anodizing over chemical blackening when you need a reliable, uniform finish. ([AR15][5]) * **If possible try to source older-style selenium-oxide (or selenious-acid + simpler acid) blackeners privately or from specialized suppliers.** But be aware: such chemicals are more hazardous and harder to ship/obtain today because of toxicity and disposal requirements. The very technical literature warns about toxicity and regulatory restrictions. ([Free Patents Online][4]) --- ## My view: Your observation makes sense it's not just user error Given the anecdotal reports, the chemical analysis of the current formula, and what early patents/literature on selenium-based blackening describe, it's quite plausible the "old version worked better" and that the weaker results now are due to a change in formulation (more acids/salts, less aggressive selenium chemistry). If you like, I can try to dig up **(publicly available) old formulations** of aluminum blackeners (pre-2010 era) used by gunsmiths or industrial finishers maybe there's one still accessible or you can mix something similar at your own risk (with appropriate safety precautions). Do you want me to start that search now? [1]: https://noordametals.com/wp-content/uploads/2017/07/Aluminum-Black-Metal-Finish-Birchwood-Laboratories.pdf?utm_source=chatgpt.com "MATERIAL SAFETY DATA SHEET" [2]: https://www.ar15.com/forums/armory/Why_does_birchwood_Casey_aluminum_black_get_such_bad_reviews/19-376970/?utm_source=chatgpt.com "Why does birchwood Casey aluminum black get such bad reviews > Refinishing > AR15.COM" [3]: https://www.freepatentsonline.com/4728365.html?utm_source=chatgpt.com "Room temperature blackening solution - Mitchell Bradford International Corp." [4]: https://www.freepatentsonline.com/9039821.html?utm_source=chatgpt.com "Methods and compositions for coating aluminum substrates - BIRCHWOOD LABORATORIES LLC" [5]: https://www.ar15.com/forums/t_3_118/362056_Birchwood_Casey_Aluminum_black.html?utm_source=chatgpt.com "Birchwood Casey Aluminum black > AR Discussions > AR15.COM" |
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The stuff on the left works vastly better than the current crap on the right. Stuff on RT, you dab and dab and dab, and eventually it starts half-heartedly doing something. It rarely gets very black, though. The stuff on the left? The aluminum turns black the instant you touch the liquid to the aluminum. Gets much blacker, stays black better. Works as claimed. Attached File |
| The AI info seems to indicate that, but it sure works better. I'd rather take my chances with something that works. It isn't like i'm putting that stuff on with my fingers. Another difference is the water base of the newer one - you can see the water surface tension as you're trying to apply it - it doesn't flow as well. |
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Dang, I just tossed some in the trash... It was from the 90's and just about all gone. The plastic bottle was all encrusted with some corrosion looking stuff that ain't normal to plastic... before I tossed it there was just enough left to wet a rag and rub it on some fresh cut aluminum... it instantly turned black. So is there another source for the good stuff? |
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Some casual Googling suggests one of these might be the best performer today. Not sure which one though. (They do offer a concentrate.) https://jaxchemical.com/product-category/blackeners/ |
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Quoted: Some casual Googling suggests one of these might be the best performer today. Not sure which one though. (They do offer a concentrate.) https://jaxchemical.com/product-category/blackeners/ Their product page also says this, which is interesting - sometime less is more, at least with their product. I should try a bottle and see how it compares with Birchwood Casey. If left for too long the Aluminum Blackener will rub off the metal easily. Practice and experience will help you find the right timing for your work. https://jaxchemical.com/shop/jax-aluminum-blackener/ |
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I may order that, although it's quite an investment, compared to buying the bottles. I also wrote to Birchwood Casey about it. Like so many other once-great brands, they have been bought up by a conglomerate (GSM Outdoors), and products and service always go out the window when that happens. After 3 or 4 back-and-forth emails with an empty-headed drone there, and him repeatedly asking the same foolish questions about products he clearly had no clue about (not even the product or what it is), he finally came back with this empty gem: The changes we have made to the product are based on regulatory industry updates to comply with environmental and safety regulations. These updates are aimed at ensuring that our products are safe for consumers and the environment. We understand that changes in formulation can affect performance, and your feedback is valuable to us. Please know that we continually strive to improve our products while adhering to these necessary regulations. I probably should order that stuff from ebay. |
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Had an AR lower NFA engraved a couple years ago. Bought a fresh bottle of BC Aluminum Black. The engraving was fresh and degreased. The BC product did nothing. Maybe a slight greying but even that seemed to wipe off with a little oil and some rubbing. Whatever the “new stuff” is, it doesn’t work. I threw the rest of the bottle out. |
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I've used Sheath for years and love it... they renamed it to 'Barricade' but I've yet to see it (but haven't looked as i still have some in the old can)... So what is the new goto product for aluminum black? I got some fresh pockets to darken and don't want to use bbq black. |
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I bought some of that Selenium Dioxide from ebay. I have not yet tried it. I'll have to do that and report back as to how well it works. I'd say it's pretty clear from the experiences detailed in this thread that BC changed the formula to something that doesn't work nearly as well, and just kept quiet about it and hoped people wouldn't notice. Pretty shameful behavior, but that's MBA corporate America for you. |
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Quoted: I've used Sheath for years and love it... they renamed it to 'Barricade' but I've yet to see it (but haven't looked as i still have some in the old can)... So what is the new goto product for aluminum black? I got some fresh pockets to darken and don't want to use bbq black. The new aluminum black isn't worth the bottle it's in, it simply does not work even when the metal is prepped according to Birchwood's instructions. What blackening you do get rubs off easily. In my experience, none of their metal finishing products work as well as they used to including the cold bluing or the copper blackening. I would be interested in finding the older formulas (a lot of stuff could be legally and safely reverse engineered by an amateur chemist if you can get a formula but it's hard to get proper laboratory glassware which is needed for a lot of chemistry). Birchwood renamed Sheath to Barricade and while it's similar it's not the same formula either. Scroll down to the "COMPOSITION & INGREDIENT INFORMATION" section. https://www.birchwoodcasey.com/content/datasheets/Barricade%20Aerosol.pdf https://www.birchwoodtechnologies.com/wp-content/uploads/2022/03/8200_Sheath_RB1_SDS.pdf |
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