What Does a Buyer Need to Know About Dow Corning Silicone?
When I first started managing industrial supply orders, I assumed all silicone was basically the same. I'd just search for "silicone sealant" and pick the cheapest option. That was a mistake. After a few expensive reorders and some awkward conversations with our engineering team, I learned that Dow Corning silicone isn't just a brand—it's a category with specific properties for specific jobs.
This guide answers the questions I wish I'd asked before my first order. If you're handling purchasing for a manufacturing facility, maintenance team, or even a small workshop, this should save you some headaches.
Is Dow Corning the Same as Dow? And What's With the Name Change?
This confused me for a while. Dow Corning was a joint venture between Dow Chemical and Corning Inc. In 2016, Dow bought out Corning's share. Then, in 2020, the combined entity rebranded its silicone business as Dowsil™. So, the products you know as "Dow Corning 732" are now officially Dowsil 732.
Does this matter for ordering? Kind of. Older spec sheets and maintenance manuals will still say Dow Corning. But if you're ordering from a distributor, you'll want to search for the Dowsil name as well. Some catalogs list both; others have fully updated. Missing this detail could mean the difference between getting your order in a week or a month. (Should mention: a lot of the core manufacturing hasn't changed, just the label.)
What Do All the Dow Corning Numbers Mean? (732, 795, 340, etc.)
This was the biggest learning curve. The numbering system isn't arbitrary—it tells you about the product family and its primary use case.
- 700 series (732, 734, 736, etc.): General-purpose sealants and adhesive sealants. The 732 is probably the most common; it's a multi-purpose neutral cure sealant. 734 and 736 are flowable versions for different application methods.
- 900 series (995, 791, 795): Structural and high-performance building sealants. The 995 is a structural glazing sealant used for bonding glass in curtain walls. Not what you'd grab for a quick plumbing fix.
- 300 series (340, 316): Thermally conductive products. The 340 heat sink compound is a classic example. It's not a sealant—it's a paste designed to transfer heat from electronics to a heatsink.
- 100 and 200 series: Often greases and fluids (like Molykote or high-vacuum greases).
Once you know this basic map, you can look at a number and get a general sense of what it's for. I still check the datasheet every time, but at least I'm not ordering a structural sealant when I need a heat sink grease.
Can I Use Dow Corning 732 Silicone Instead of 795?
I've been asked this more times than I can count. The short answer: probably not, unless you like doing things twice.
Here's the deal. The 732 is a general-purpose adhesive sealant with a tensile strength of about 260 psi (per the technical datasheet). It's great for sealing gaps, bonding non-structural components, and general maintenance. The 795 (now Dowsil 795) is a structural sealant with a tensile strength of 450+ psi, specifically tested and certified for structural glazing and curtain wall applications. They're rated for different wind loads and movement capabilities.
Using 732 where 795 is specified is like using wood glue to hold up a bookshelf. It might work for a bit, but you're taking a risk. I once had a project manager argue for the cheaper 732 "just this once." It didn't end well. The replacement cost was triple the material savings. At least, that's been my experience with building envelope projects—your mileage may vary.
How Do I Choose Between Different Dow Corning Black Silicone Options?
This is a common search, and I get it—black silicone looks good and hides dirt. But "black silicone" isn't a single product.
- Dow Corning 732 Black: Multi-purpose, good for bonding and sealing where appearance matters. Common for equipment assembly and gasketing.
- Dow Corning 3140 RTV Black: A much softer, lower-modulus adhesive. Used for more flexible bonds where thermal expansion is a concern.
- Dow Corning 340 Black (Heat Sink Compound): This isn't a sealant at all. It's a thermal paste. Putting it on a seam won't seal anything. I've seen that mistake.
Check the datasheet for cure time, operating temperature range, and whether it's a one-part or two-part system. If your project involves sensitive electronics, make sure it's a neutral cure (non-corrosive) formulation.
What Does a Silicone RTV Number Mean? (And Why Should I Care About Durometer?)
RTV stands for Room Temperature Vulcanizing. It means the silicone cures (solidifies) at room temperature without needing heat. The number after RTV (like RTV 100 series) often correlates with the durometer, which is a measure of hardness.
Why durometer matters: If you're sealing a joint that vibrates, you want a softer silicone (lower durometer) that can flex without cracking. If you're potting an electronics assembly for shock protection, you might want something firmer. The Dow Corning RTV datasheets always list durometer in Shore A. A lower number (like 20-30) is soft and rubbery. A higher number (50+) is firm and rigid.
When you see a spec like "durometer o ring," you're usually talking about the hardness of an O-ring material, which can be silicone. Standard O-rings are often 70 Shore A. If you're substituting a silicone sealant for a pre-made O-ring, make sure the cured durometer is in the right range, or your seal will leak.
Can I Get Genuine Dow Corning Silicone in Small Quantities?
Yes, but you'll pay a premium. The bulk pricing for a 10.3 oz tube (like the standard 732 cartridge) is efficient. Once you start needing smaller tubes or specialty kits, the per-ounce cost goes up significantly. I've also seen counterfeit products on general marketplaces—look for authorized distributors and check the batch numbers if you can.
For one-off repairs, a standard tube is usually fine. For large-scale sealing projects like a warehouse roof, you'll want 5-gallon pails or 55-gallon drums. That's when you negotiate on price and make sure the invoicing is clear. I learned that after a vendor sent a handwritten receipt for a $1,200 drum order, Finance rejected it, and I had to use my department budget to cover it.
How Does Silicone Compare to Other Insulation Foams? (Like Foam Board vs. Spray Foam)
This isn't directly a silicone question, but it's related. Silicone sealants are often used in insulation systems to seal gaps and joints. You might be choosing between a silicone sealant and an expanding foam for air sealing.
Here's the trade-off I've seen: Spray foam provides excellent insulation (R-value of about 6.0 per inch for closed-cell). But it's messy, difficult to remove, and can over-expand and warp door frames. Foam board is rigid and has a consistent R-value (R-5 to R-6 per inch), but it needs to be meticulously taped and sealed at the joints. Silicone sealant (like Dow Corning 791) is used to seal those joints and around penetrations. It doesn't have significant insulating value on its own, but it stops air leakage, which is where a lot of heat loss actually happens.
My take: they're complementary, not competitors. Insulation is the blanket. Silicone sealant is the zipper. You need both for the system to work. I wouldn't use silicone as a primary insulator, and I wouldn't trust spray foam alone to seal a moving joint.
What's the Most Common Mistake Buyers Make with Dow Corning Products?
The biggest mistake I see—and made myself—is ignoring the cure time and skin-over time. Just because it's applied doesn't mean it's ready.
- Skin-over time: How long until the surface isn't tacky (typically 10-30 minutes for standard neutral cure).
- Cure time: How long until it reaches full mechanical properties (often 24 hours for a 1/8" bead, but thicker takes exponentially longer).
I once had a wrenching shop apply a silicone gasket maker on a Friday, reassembled the part Saturday morning, and had a leak on Monday. The datasheet said 24-hour full cure. They gave it 12. The bond failed under pressure.
Also: check the shelf life. Dow Corning products have a stamped date code. Even unopened, the catalyst system degrades over time. Old silicone won't cure properly. Check the date before you accept the order.
One more thing: acetic acid cure (the ones that smell like vinegar) can corrode some metals and electronics. Neutral cure (oxime or alkoxy) is safer for sensitive substrates. Always confirm this before ordering if you're working with copper, brass, or circuit boards.