Look across our epoxy range and you'll notice the mix ratios aren't all the same: some resins are 2:1, others 5:1, and specialist casting resins run at 3:1 or even 1:1. That's not inconsistency, and it's not something you can change by measuring differently. The ratio is fixed by the chemistry of that specific resin and hardener pairing, and it tells you a lot about what the system is actually built to do.
2:1 — The Non-Blushing Workhorse
Our MAS Low Vis Resin and MAS FLAG Thick Resin are both mixed at a simple 2:1 ratio by volume, and both belong to the same wax-free, non-blushing system. That's the biggest practical difference between this system and a traditional epoxy: there's no amine wax forming on the surface as it cures, so you can skip the wash-and-sand step between coats. If you want the full explanation of why that matters, we've covered it in detail in our guide to amine blush.
Within the 2:1 system, Low Vis and FLAG serve different jobs. Low Vis is formulated to soak in, making it the better choice for wetting out fibreglass cloth and saturating porous timber. FLAG is formulated to stay put, with a thicker bond line and better sag resistance, which makes it the right call for vertical or overhead gluing and laminating. The two are fully compatible and can be blended together if you want a viscosity somewhere between the two.
5:1 — The Traditional Structural System
MAS Boat Building Epoxy 5 to 1 Slow is the ratio a lot of boat builders learned on, and it's still a dependable choice for structural lamination, hull and deck bonding, and general marine repair. It's a traditional amine-cure system rather than a non-blushing one, so the usual wash-and-sand routine between coats does apply here. What you get in return is a proven, self-levelling resin that bonds well to timber, fibreglass, bare steel and lead, with a slow hardener giving a longer working window for bigger lamination jobs.
3:1 — Built for Deep Pours
MAS Deep Pour Casting Epoxy uses a 3:1 ratio for a completely different reason to the resins above: heat management. Deep pours generate far more exotherm than a thin coat, and this system is formulated with an extended gel time specifically to reduce that heat build-up and improve air release, so a thick pour cures clear rather than cracking, yellowing, or shrinking. It's a specialist resin for a specialist job — river tables, encapsulations, and thick castings — not a general-purpose structural epoxy.
1:1 — Fast, Simple, and Application-Specific
A handful of our products use a straightforward 1:1 ratio, and each does for a different reason. MAS Fairing Compound is 1:1 with colour-changing verification, so you can see at a glance once it's properly blended, which matters when you're mixing small batches repeatedly through a fairing job. MAS Art Pro Epoxy is also 1:1, giving resin artists a simple, repeatable ratio with a 60-minute working time to build high-gloss pieces.
So Which One Do You Need?
As a rough guide: reach for the 2:1 system (Low Vis or FLAG) for laminating, coating, and general boat building where you'd rather not wash down between coats; go 5:1 if you're working to a traditional structural system; use the 3:1 Deep Pour system only for genuine deep pours rather than thin coats; and pick a 1:1 product when the job is fairing or resin art rather than structural work. If you're still not sure which system suits your project, our full epoxy range breaks each product down by what it's built for, or get in touch via our contact page and we'll talk it through.
