Simon Liu Inc.

Canvas Stretchers

Whether refining venerable classics or pioneering fresh innovations, we never stop obsessing over all the minor details that go into building exceptional stretchers.

Understanding your Canvas Stretcher options

While some clients arrive knowing exactly what they need, and why, others can find all our Canvas Stretcher choices and features difficult to unpack. Please know that direct questions and inquiries are always welcome. We enjoy the process of close, creative collaboration with clients and strive to meet their objectives and budgets whenever possible. 

But to get a general sense of all the options and their particular attributes, it’s also instructive to take a look back at how canvas stretchers have evolved. (And you can scroll down to our stretcher types at any point.)


Once the advantages and conveniences of painting on canvas were realized around the late 16th and early 17th century, the challenge of building durable yet relatively lightweight Canvas Stretchers became the next frontier in art supports. And in some ways, that hasn’t changed.

With new forays into composite materials and manufacturing techniques, stretcher design and construction continue to evolve. But not every new approach has necessarily marked an improvement in quality. For example, the Smithsonian has learned over time that certain once-promising plastic materials, previously presumed safe and relatively permanent, are now deteriorating before anyone thought possible. 

With any artwork on canvas, the primary adversity has always been how the fabric will absorb moisture and expand. This natural stretching and sagging, occurring with varying degrees of severity depending on environmental and other factors, will invariably take its toll on an artwork, particularly layers of oil paint. 

Overall, with the hindsight of conservators and restoration sciences now extending back hundreds of years, we know a great deal about the consequences of time and the elements on stretched canvas and various woods. 

Based on that knowledge, Simon Liu’s approach is based on serving longevity and aesthetics. 


By roughly the middle of the 18th century, it was clear that the fixed joinery of the earliest stretcher designs represented a serious limitation. To compensate, keying was invented to allow for expandable joints. 

Keying can take various forms, but its functional role is to endow a stretcher with built-in maintenance potential that allows for adjusting the canvas tension in small increments. 

Otherwise, a fixed frame (or strainer) all but ensures that the artwork will have to be restretched and reframed at some point.

 The earliest keyed stretcher designs were less than perfect, but the craft and components of keying gradually became more sophisticated and secure.

 Simon Liu’s personal keying designs and innovations have all stemmed from the principle that there is always room for improvement, even within traditional canvas stretcher forms.


In the early, pre-industrial days when every stretcher was slowly built by hand, it’s fair to say that accuracy and precision suffered even when the craftsmanship was exceptional. Eventually, that problem reversed.

With the 19th century came the advent of commercially produced canvas stretchers. Critical design improvements resulted, but individual craftsmanship went into decline. Machines could churn out relatively consistent, inexpensive canvas stretchers in great numbers, but the diminished integrity of the materials and erosion of quality control standards spawned problems that harmed artworks over time, introducing a new set of challenges for conservators in the generations to come.

Keyable Stretcher - Simon Liu Inc.

Our unique approach to building Canvas Stretchers

Our semi-boutique production process, merging the power of customized tooling with the added precision and quality control of veteran artisans, is a best-of-both-worlds model distinct from the world of mass-produced, store-bought options.

We cut our canvas stretchers using machine technology and tools, but purposefully work on a small manufacturing scale that prioritizes the human factor, with the skill and eye of an experienced craftsman vetting every measurement, every piece of wood, every joint.

In all our products, but especially when it comes to building larger stretchers, the precision and strength of our wood joinery cannot be matched anywhere. 

Features of our Canvas Stretchers

The unsurpassed reliability we achieve with each Canvas Stretcher breaks down largely to the quality of the materials and the strength and precision of the design.


Wood quality is paramount. We meticulously source and scrutinize every piece of wood that enters our studio. Clear lumber is key and, in our experience over three decades, only certain woods are suitable for making stretcher bars.

Most types of wood will twist to some degree as they age and, unfortunately, finding sufficient quantities of the woods we trust, at the quality grade we demand, has become increasingly difficult over time.

This only means we strive harder to ensure the exceptional.


Sugar Pine is our main canvas stretcher material: a western softwood distinguished by excellent workability and texture. Though categorized as a softwood, Sugar Pine is actually fairly hard for a pine and named “Sugar” thanks to its unique, sweet resin, which helps to protect the wood from decay.

Featuring a straight, uniform grain, Sugar Pine is lightweight and fairly clear with relatively knot-free properties. The density and strength make it structurally dependable while its fine surface texture supports exceptional finishing and staining results. (And for panels, it provides a highly smooth painting surface.)


The basswood tree yields lumber that is fairly soft for a true hardwood. Once seasoned, it remains remarkably stable and nearly impervious to warping or twisting even over long periods of time.

The grain tends to be notably fine, straight, and uniform while, overall, like Sugar Pine, Basswood is a potent blend of strong and stable despite being lightweight.

From there, building quality stretcher bars becomes about crafting the right profile.


Among the various technical features of canvas stretchers, understanding stretcher bar profiles can be a challenge. What are the advantages of a continuous bevel? Why select an L-shaped profile?

For one thing, there always has to be some degree of a stretcher bar bevel, even just a slight one, to separate the canvas from resting directly on the stretcher, which can cause aesthetic problems to the canvas surface, especially over time.

Similarly, the crossbars are always set back a ways, so they don’t become visible through the canvas.

A continuous bevel supports thinner profiles. And with work from the 19th century and older, a thinner profile is often necessary to fit the piece in its frame and conservators will require a thinner profile.

An L-shaped profile, on the other hand, is usually very deep, providing more separation. This is more common for modern or contemporary work.

A thinner profile will be more resistant to twisting, but another hedge that’s worth incorporating is sealing your stretcher bars.


While sealing is not an absolute necessity with Canvas Stretchers, we still recommend the added protection it provides. Whether using a clear shellac, or B-I-N®, a white, shellac-based primer-sealer, or Camger, a water-based polyurethane, sealing the wood helps prevent drying out and reduces significantly the possibility of future twisting.

All wood will invariably move at least slightly over great lengths of time, and nothing is fool-proof. But sealing fortifies stability considerably.

Canvas Stretchers | Simon Liu Inc.

Simon Liu Inc.

Canvas Stretcher Types

For most artists and many conservators, our American Traditional Stretcher, Mechanical Stretcher, or relatively new and innovative Aluminum Stretcher options will meet their art support needs.

However, with the same uncompromising dedication to quality and longevity, we also build more specialized varieties. Most often coveted by conservators, these options include our Italian Style Stretcher, French Style Stretcher, Modern Traditional Stretcher, and more.

American Traditional Stretcher - Simon Liu Inc

American Traditional Stretcher

Great for artists, great for conservators, this stalwart art support remains the most popular stretcher in the United States. Invented in the late 19th Century, the American Traditional is distinguished by keyed double-finger miter joints for the corners, with keyed mortise and tenon joints for the crossbars –– so it's a 100% keyable stretcher. It also features the most versatile joinery, making it easier for customers to piece together on their own if they prefer. Simon's contribution to this classic has been to refine with customized tooling the American Traditional joinery in a way that preserves its original design while still improving functionality and strength.

Specifications: Featuring hardwood keys, Simon Liu’s American Traditional stretchers are handcrafted in either sugar pine with a continuous bevel or in basswood with an L-shaped, tongue-and-groove profile.

Mechanical Stretcher

Less expensive than the American Traditional but comparably tried and true, Simon's take on James Lebron's enduring invention is a painting support built to remain perfectly square. The Mechanical Stretcher's adroit design uses Tite-Joint™ fasteners and two aluminum guiding pins for the connecting miter and butt joint. Extending the fasteners tightens the canvas. Once the proper tension is achieved, wood shims placed between the hardware and guiding pins hold the tension while the hardware is tightened to stabilize the joint. Mechanical Stretchers are available in both wood and aluminum.

Specifications: We have two profiles. Our continuous bevel option is constructed out of sugar pine while our L-shaped profile is produced with basswood in various thicknesses.

Aluminum Stretcher - Simon Liu Inc.

Aluminum Stretcher

Aluminum options represent the next frontier in canvas stretchers. Good, stable, quality wood is increasingly difficult to source and supplies can only be expected to dwindle further. Even discounting that consideration, aluminum's superior stability makes it an appealing material, albeit one with certain limitations and issues to be managed. Once again, Simon Liu's approach is to innovate. In this case: premium aluminum and wood hybrids. Entirely aluminum-on-aluminum stretchers don't hold together well, with some degree of movement no matter how tight the bolts. As a softer material, wood grips far better. In addition, a wooden lip outside an aluminum body allows for diverse sizing and styles. It also provides an area for staples and protects the canvas from water condensation. (Aluminum introduces moisture from water condensation whenever a piece goes from a cooler, dryer environment to increased humidity and heat.) And for mural-sized pieces, an aluminum stretcher with a wooden lip provides the best way to align the two tabs of a folding stretcher.

Specifications: We are designing and building custom-order items for clients interested in aluminum options.

Shaped Stretcher & Strainer - Simon Liu Inc.

Shaped Stretcher & Strainer

Custom orders can accommodate a wide range of atypical or irregularly shaped pieces with either a strainer or keyable stretcher. Most commonly, these options are round or oval, though difficult challenges with unusual shapes are one of our specialities.

Specifications: A wide range of options depending on the piece.

Italian Stretcher - Simon Liu Inc

Italian Style Stretcher

A specialty option typically for conservators, our Italian Style stretcher is a modification of a mid-19th-century design, featuring a simple closed mortise and tenon joint with interlocking forked key. This centralized-joint setup provides superior grip for the keys and therefore minimal torque when keying out. Specifications: Features an L-shaped biscuit joint at the corners

French Stretcher - Simon Liu Inc

French Style Stretcher

Another rare specialty option. Conservators turn to our French Style stretchers for the highly accurate, reliable restoration of period pieces. Originally popular in late-19th-century France, the design features a miter joint on the face and a butt joint on the back (departing from earlier versions with a mortise and half miter construction). Simon's modification, incorporating an extra finger in the joint, provides additional strength.

Specifications: Available in a flat back continuous bevel profile or a bevel back continuous bevel profile. Made with sugar pine and basswood for the crossbars.

Single Pin Stretcher - Simon Liu Inc.

Single Pin Stretcher

A very rare option, the single pin design — a thin, narrow profile with one pin fastener per corner — is ideal for artists looking to displaying two works back to back or for creating smaller sized pieces. Our single pin stretchers utilize Tite-Joint™ fasteners with a single guide pin.

Specifications: We offer two profiles. The flat back continuous bevel profile works well for small-sized pieces while the flat profile is perfect for double-sided painting.

Independent Keying Stretcher - Simon Liu Inc.

Independent Keying Stretcher

Like the Mechanical Stretcher, the Independent Keying stretcher utilizes Tite-Joint™ fasteners, only doubled up, with two (one on each side) for each corner. This system affords greater options for targeted keying while maintaining a stronger joint.

Specifications: A flat back continuous bevel profile; an L-shaped tongue and groove profile; or an L-shaped biscuit joint profile. Wood shims provide optimal keying.

Get a custom quote for your stretchers