Canvas Stretching and Custom Strainers & Stretchers

Strainers and Stretcher Samples - Note that we now use Richeson BEST Corner Keys but haven't updated)

At SecondMoonshot Custom Picture Framing, serving artists, collectors, and photographers across Rolesville and Wake Forest, NC, we have expanded our services to offer specialized, conservation and preservation-level canvas stretching. Proper canvas stretching demands careful tension management and structural precision to prevent sagging, warping, or surface cracking over time.

Rather than relying on a one-size-fits-all model, we provide flexible, research-backed structural options designed to meet the exact scale, display environment, and longevity requirements of your artwork. Our lineup includes premier Complete Aluminum-Wood Hybrid Stretcher Bars from Jack Richeson Art as well as custom frameworks built in-house utilizing precision Jack Richeson BEST Corner Keys. Every project receives a detailed, itemized quote outlining exact profile dimensions, wood species, mounting methods, and transparent costs—all backed by our Lifetime Workmanship & Materials Guarantee.

In this section, we focus specifically on our custom in-house built stretchers and strainers, examining how each option is constructed to ensure long-term stability for your canvas.

What is the Difference Between a Stretcher and a Strainer?

When mounting canvas artwork, selecting the proper internal framework is essential for maintaining surface tension and ensuring long-term structural integrity. While both strainers and stretchers provide a solid foundation for canvas stretching, their corner mechanics serve distinct preservation and functional needs.

Strainers: Fixed, Non-Adjustable Frameworks

Strainers feature precision-mitered corners that are permanently joined during construction. Because the overall dimensions of a strainer are static, the frame cannot be expanded once assembled.

• Tension Control: If the canvas relaxes or loses tension over time, re-tightening requires removing the perimeter staples and manually re-stretching the fabric across the frame.

• Ideal Applications: A strainer is a practical, reliable choice for rigid or heavy-weight canvases that resist movement, as well as artwork that was previously stretched but unmounted for shipping or transport.

• Craftsmanship & Investment: Strainers require less complex corner joinery and no internal expanding hardware. At SecondMoonshot, opting for a custom strainer typically reduces the build investment by approximately $100 compared to an expandable stretcher. This cost difference reflects the specialized labor and corner hardware required for adjustable frames, regardless of the overall dimensions.

Stretchers: Dynamic, Expandable Tension Systems

Stretchers feature dynamic corner joinery designed to allow post-installation tension adjustments. Rather than remaining locked in place, the corners can be expanded outward to maintain ideal surface tautness.

• Adjustment Mechanics: While standard commercial stretchers use small wooden keys inserted into mortises, our in-house custom stretchers utilize an integrated turnbuckle system at each corner. Expanding the turnbuckles gently forces the corners outward, restoring drum-tight canvas tension without disturbing the artwork or removing staples.

• Environmental Protection: Natural canvas fibers continuously expand and contract in response to humidity and temperature fluctuations in the Rolesville and Wake Forest climate. Dynamic stretchers allow for ongoing fine-tuning, preventing canvas sagging or stress-induced paint cracking over decades of display.

• Build Complexity: Due to the precision joinery, hardware integration, and multi-step assembly required for expanding corners, custom stretchers represent a higher level of workshop labor and material complexity.

The Construction

Premier Timber Selection: Basswood

We build our custom strainers and stretchers exclusively from select Basswood. Basswood serves as the premier timber choice for custom canvas support frameworks due to its exceptional dimensional stability, high strength-to-weight ratio, and tight, uniform grain structure.

Unlike common construction-grade softwoods, pine or yellow poplar—which often harbor internal growth stresses, uneven grain patterns, or active sap that can warp frames and leach into raw textiles—Basswood resists bowing, twisting, and cupping under high canvas tension. Its neutral properties and low resin content safeguard delicate cotton and linen fibers against long-term material degradation, while its ability to remain flat through North Carolina’s seasonal humidity shifts makes it a reliable, research-backed foundation for conservation and preservation-grade artwork presentation.

Precision Engineering Across Sizes

Every custom strainer and stretcher begins with the same foundation of precision-milled Basswood, with profile dimensions tailored to the specific depth and scale requirements of your artwork.

• Larger Stretchers & Strainers (2-Part Construction): For larger canvas dimensions, we utilize a robust two-part assembly. This profile is built from two pieces of milled 3/4" Basswood glued and fastened perpendicularly. Joining the wood at right angles leverages counter-grain strength to eliminate natural lumber bowing and resist twisting under high tension across long spans.

• Smaller Stretchers & Strainers: Smaller frameworks are crafted using a solid 1" wide Basswood strip, providing proportional support without adding unnecessary weight to smaller displays.

Profile Beveling & Edge Finishing

To ensure the stretched canvas remains protected and visually pristine over time, every outer frame edge undergoes specialized profiling:

• 15-Degree Relief Bevel: The outer top face of the wood is cut with a 15-degree bevel. This slopes the frame inward, ensuring the canvas fabric makes contact only at the outermost perimeter edge and never rests flat against the inner wooden frame.

• 1/4" Rounded Router Pass: The top outer corner receives a 1/4" rounded router pass to soften the transition, preventing shear stress or cracking along painted canvas borders.

• Hand-Sanded Finish: All sharp corners and outer surfaces are thoroughly hand-sanded to ensure smooth edges that will not snag or fray delicate textile fibers during stretching.

Profile View of our Strainer and Stretcher Bar

For our custom strainers, we miter the corners and join them using PVA wood adhesives and pneumatic V-nails for a seamless, structural bond. On larger frameworks, we integrate internal cross-braces every 30 to 36 inches, secured with pocket screws and glue, to prevent long-span bowing under canvas tension. For oversized strainers, we install custom wooden corner braces to ensure the assembly remains square, flat, and structurally sound over time.

Strainer with Wooden Corner Brace

Strainer with Cross Brace secured with Pocket Screw and Glue

For stretchers, we will mitre the corners just like for the strainer. We then will drill two 1/4" holes perpendicular to the mitre cut. These holes will hold aluminum dowels (with opposing sides secured so they can slide smoothly and retain the shape when tightening). This is not a new design and was originally published in the 1960s by James Lebron. The diagram below came from The Grumble and I think it was posted by "wpfay" user and modified the original design slightly.

Overview of the Adjustable Corner System

While our initial prototype utilized 45-degree angled turnbuckles, our standard production stretchers feature Jack Richeson BEST Corner Keys for smooth, expandable corner tensioning.

To adjust canvas tension over time, simply turn the expansion hardware equal amounts at each of the four corners. Repeating this uniform sequence around the frame gradually expands the corner joinery, restoring drum-tight canvas tautness safely and evenly without stressing the canvas fibers or disturbing the artwork.

Corner Key Not Expanded

Corner Key Expanded

Once the strainer or stretcher framework is fully assembled, we seal the wood by hand-applying Zinsser SealCoat, a 100% wax-free dewaxed shellac. Sealing raw timber is a critical step in conservation and preservation-grade framing. Unsealed wood naturally off-gasses organic acids and lignins over time and can absorb ambient humidity, causing subtle dimensional swelling or warping.

By applying a dedicated, non-reactive seal coat, we create a protective barrier that seals in natural wood resins and tannins—preventing them from migrating into the raw canvas fabric. Additionally, this non-hygroscopic seal inhibits seasonal moisture absorption through North Carolina’s humid cycles, ensuring your custom support structure maintains its dimensional stability and structural integrity for a lifetime.

Getting ready to seal a pair of strainers for a smaller canvas print.

That outlines our core in-house build process. For large-format artwork, high-span canvases, or delicate pieces requiring maximum dimensional stability, we also offer Jack Richeson Hybrid Wood Aluminum Pro Stretcher Bars. This specialized system incorporates the same precision turnbuckle expansion mechanics as our custom wooden stretchers, but pairs a outer wood pinning border with a rigid aluminum interior framework. The result is a lighter, ultra-stable structural core that completely eliminates twisting or bowing over long spans.

Author's Note: A portion of this content was authored with the assistance of AI, mostly for wordsmithing my original technical notes.

Disclaimer: Any links provided are direct links. SecondMoonshot is not an affiliate for any manufacturer, product, or service referenced. We independently purchase and use the products and services mentioned.