If you’ve ever worked with brass foil for electrical components, decorative metalwork, mechanical gaskets, or even custom craft projects, you’ve probably run across the term “RA brass foil” at some point. As a supplier who’s spent 12 years working directly with metal fabricators, electronics engineers, and small-batch custom makers, one of the most common questions I get isn’t about thickness (though that’s important!)—it’s about density. People want to know exactly what the density of RA brass foil is, how it compares to other brass alloys, and why that single number matters enough to call or email us about. Today I’m breaking this down clearly, sharing what we’ve learned from decades of supplying RA brass foil, and explaining why density isn’t just a random stat—it’s a critical detail for getting your project right. RA Brass Foil
First, let’s start with a quick, plain-language definition of RA brass, since that’s the foundation of the foil’s density. RA stands for “Rolled Brass,” and that’s not just a label. Unlike cast brass, which is poured into molds and then machined, RA brass is produced by repeatedly rolling solid brass ingots through heavy metal presses at controlled temperatures until they’re thinned to the exact gauge you need. That rolling process aligns the metal’s grain structure tightly, creates a uniform crystalline makeup, and results in material that’s far more consistent than cast brass foil—especially in thin gauges (think 0.001 inches up to 0.020 inches, the most common we stock for our customers).
Brass itself is an alloy of copper and zinc, right? The exact ratio of those two metals is what tweaks the density, strength, and conductivity. RA brass foil is almost always a 70/30 brass alloy, sometimes called cartridge brass, because that balance works perfectly for most foil applications. 70% copper and 30% zinc gives RA brass its signature blend of malleability (perfect for rolling into thin, flexible foil), corrosion resistance, and electrical conductivity—all while keeping density steady and predictable. That consistency is why so many aerospace, automotive, and electronics teams specify RA brass foil specifically, rather than off-brand brass foils.
Now, the big question: What’s the density of RA brass foil? For 70/30 RA brass, the density is 8.53 grams per cubic centimeter (g/cm³), or roughly 0.308 pounds per cubic inch (lb/in³). I’ll admit, when I first started in this industry, I thought density was just a number from a textbook. But over the years, I’ve watched customers need that exact number on project specs, and I’ve seen what happens when someone uses the wrong density calculation. Let me explain why that matters so much.
If you’re designing a custom electrical connector, for example, you might be calculating the weight of a finished component to make sure it meets aerospace weight limits, or to balance it in a handheld device. If you use the wrong density for brass (say, the density of pure copper, which is 8.96 g/cm³, or even a lower-quality brass alloy with more zinc or impurities, which has a lower density), your final weight will be off by 5% or more. That might not sound like a lot, but in an aerospace part where every 0.1 grams counts, that’s a difference that could require a full rework of your design. We’ve had an aerospace customer call us in a panic once because their engineering team had used a generic brass density stat and their final wing component was 6% over the weight limit. We were able to walk them through using the correct RA brass density to recalculate, and they adjusted their design without missing their production deadline.
Density also ties directly to another key property of RA brass foil: its thickness consistency. Wait, how is that connected? Because density is mass per unit volume, if you know the density of the material, you can verify that a roll of foil is the exact thickness you ordered. Let’s do a quick math example: If you have a 1-square-inch piece of RA brass foil with a thickness of 0.005 inches, its volume is 1 in x 1 in x 0.005 in = 0.005 cubic inches. Multiply that by RA brass’s density (0.308 lb/in³) and you get a mass of 0.00154 pounds, or roughly 0.00246 ounces. If you weigh that piece of foil and it comes out lighter or heavier, that means the actual thickness is off—even if your micrometer says it’s on spec. We use this trick in our quality control lab every single day for bulk orders. For a roll of foil that’s 12 inches wide, 50 feet long, and 0.003 inches thick, we calculate the expected weight per roll using the density of RA brass. If the actual weight is off by more than 1%, we know there’s an issue with the rolling process, and we pull that roll for re-calibration. That’s how we’ve maintained a 99.8% on-spec rate for our RA brass foil over the past decade—small, consistent checks using density paired with traditional thickness measurements.
Another common place RA brass density comes into play is in decorative metalwork, like custom brass accents for furniture, hardware, or art pieces. Many artists and small woodworkers come to us because they want a foil that will hold a uniform finish, and density plays a role here too. Lower-density brass alloys often have tiny gaps or impurities in their crystalline structure that can cause paint, patina, or lacquer to apply unevenly. RA brass’s uniform density (thanks to the rolling process) means a smooth, consistent finish every time. I’ve had a furniture maker client who’s worked on high-end residential projects tell me he only uses our RA brass foil because the patina never comes out splotchy, unlike cheaper foil he’s tried in the past. He attributed that to the consistent density, and after explaining that RA brass’s rolling process eliminates internal gaps, it all made sense to him.
Wait, should we address any common misconceptions about RA brass density? Definitely. A lot of people assume all brass foil has the same density, or that RA brass density changes with thickness. That’s not true. The 8.53 g/cm³ density is a physical property of the RA brass alloy itself, regardless of how thin the foil is rolled. We’ve supplied RA brass foil as thin as 0.001 inches (that’s 1 mil, thinner than a piece of paper) and as thick as 0.020 inches (20 mil, rigid enough for small gaskets), and we test the density of every gauge to confirm it stays consistent. The only time you’ll see a density variation is if the foil is a different brass alloy, or if it’s not truly RA brass (i.e., it’s cast, or made with a different copper-zinc ratio). Some budget brass foils add small amounts of lead or other cheaper metals to cut costs, and those can lower density by 2-5%—but that’s not true RA brass, and it’s not something we supply, because those impurities ruin the consistency our customers rely on.
I also want to mention that density is one of the reasons RA brass foil is preferred over other types of thin metal foils for critical applications. For example, aluminum foil has a density of only 2.70 g/cm³—about a third of RA brass’s density. While aluminum is lighter, it doesn’t have the same tensile strength or corrosion resistance as RA brass, and its lower density means it can’t hold up under the pressure of repeated bending or high temperatures. Copper foil has a higher density (8.96 g/cm³) but it’s less malleable for thin gauges, making it harder to work with for intricate parts. RA brass hits that sweet spot: a density that gives it durability and consistent weight, while still being flexible enough to roll into ultra-thin foil.
As a supplier, we also make sure to include density specs on all our product data sheets, because we know how important that number is to our customers. Whether you’re a mechanical engineer calculating component weight, a craftsperson needing uniform material for a custom project, or a manufacturer running quality checks on bulk orders, having the exact density of your material eliminates guesswork and reduces the risk of costly mistakes. We’ve had customers tell us that when they switched to our RA brass foil, they were able to cut their rework rate by 10% just because they were using the correct density for their calculations. That’s the kind of impact a single, correct spec can have.
If you’re working on a project where RA brass foil is part of the equation, don’t leave the details to chance. Density, gauge, and alloy purity all make a difference, and we’ve spent years perfecting our process to deliver RA brass foil that’s consistent, reliable, and exactly what your project needs. Whether you need a small sample for testing, a custom roll size, or bulk quantities for a production run, we’re here to help you get the right material and answer any questions you have about specs, applications, or pricing. You can reach out to our team to discuss your RA brass foil needs and make sure you’re getting the density, quality, and service that will keep your project on track.
Ed Copper Foils References
- Brass Alloy Data Handbook. Copper Development Association Inc., 2021.
- Metal Foil Manufacturing: Rolled Brass Properties and Applications. Metal Processing Institute, 2019.
- Aerospace Materials Standards for Brass Components. SAE International, 2022.
Civen Metal Material (Shanghai) Co., Ltd.
Address: Workshop 2-2, No.1888 Xiechun Road, Jiading District, Shanghai, 201804, P.R.China
E-mail: sales@civen.cn
WebSite: http://www.civenmetal.com/
