Stretching without straining
The cry an artist stretcher frame maker is often met with is “why would a picture framer want to upgrade from the run of the mill under-pinned strainer frame they have been using ever since they could staple their mitres together, and convert to a stretcher frame?”
I had better start by defining the difference between an artist stretcher and a strainer frame, as it tends to be a point of confusion. An artist stretcher frame actually does what its name implies – unlike a strainer it can expand its perimeter and literally stretch the canvas tighter: taking up slack and uneven ripples in the canvas and keeping an artwork taut. Having the capability to expand the artist stretcher frame gives a framer, or the owner of a canvas artwork, the potential to re-tension a painting or print on canvas after it has loosened.
Cotton duck and linen, which are the regularly used fibres from which artist canvases are woven, are hygroscopic materials, which means they readily absorb moisture molecules from the atmosphere. This is especially the case when one surface is coated with paint and primers and the other left raw or loomstate. The effect of moisture absorption is to loosen the canvas, and hence an evenly taut painting leaves the framer and enters a humid or moist environment and becomes loose, floppy and wavy. Horror!
At this point, if the canvas is stretched on a strainer that can’t be expanded, the only recourse is to then unpick the staples or tacks and to re-stretch it. If on the other hand, the canvas has been stretched on an expandable stretcher then it’s simply a matter of gently expanding the frame.
The traditional artist stretcher is a beautiful thing! The frame uses keys or wedges that are gently tapped into a slot in the machined timber joint. The pressure exerted by the wedges slowly divides apart the two components that make up the corner, whilst the tenons hold the frame together and enable it to remain strong as the mitre joint is tapped open. It works wonderfully and has done so for many centuries, but trust me, it is difficult to machine.
The traditional artist stretcher frame utilizes quite complex joinery that is only time efficient to make yourself using multiple shaping machines. A bevy of cutters and acres of space is also required, all well beyond the economies of a regular framing business, and only practical to tool up for if you are considering mass producing these frames.
You can buy artist stretcher frames for artists and framers pre-cut to standard sizes off the shelf in art material stores or from an artist stretcher manufacturer, but the problem is how often is your painting or print just the right size for a standard mass produced frame?
A solution is to order the artist stretcher frames cut to the millimetre from companies that manufacture custom stretcher frames. But be prepared to wait for the service, and be absolutely certain to get your measurements right on the money.
Here is where the Belle Arti system steps into the picture (pardon the pun), as it can offer you the independence and benefits of manufacturing your own stretcher bars.
The process is straight forward: cut the mitre to length on your mitre saw or guillotine, and then set the depth stop on the Belle Arti machine (which if you use only a couple of profile sizes you have preset and left). You can then safely plunge the timber into the covered cutter to cut a slot in the stretcher, into which a strong heart shaped joiner is inserted into both sides of the corner that you have machined to create a firm joint. It literally takes only seconds to cut each joint, and tap the expandable heart shaped joiners into the mitred corners and you have created a good strong frame.
The heart shaped corner joiners are made of an ultra-strong plastic composite which houses a metal screw that is wound into the joiner. As the screw winds further into the thread of the heart it pushes a hardened plastic tongue that levers the mitre joint open, while still holding the frame securely together. There are two expanding tongues that enter each component of the frame giving the ability to expand the corner independently in both directions. With a simple turn of a screw you are able to expand the frame and tighten that loose canvas.
Braces can also be joined into the frame, if it is larger than a metre, by inserting oval shaped connectors to join the braces to the stretcher bars. These connectors can also be expanded to exert pressure and expand the frame out from the sides. The change over to cut the braces requires no tool changes, just easy fence stop adjustment using exactly the same cutter at the same height. The system and its hardware are simple, compact, accurate and affordable and offer to the millimetre size stretcher frame production in your workshop. It practically takes minutes to make to completion a custom size expandable artist stretcher frame. Now you are ready to stretch your image!
At this point in the process having an expandable frame enables the framer the comfort and safety of not having to stretch the artwork super tight and risk cracking paint films or printed ink. What a nightmare watching the edges crack from pulling the hell out of the canvas! Instead, just lightly pull the canvas around the frame after having accurately positioned the image and then tack or staple it to the frame. With a slight turn of the screws in the joints the tension on the canvas can be adjusted. If the canvas later loosens from atmospheric exposure, it can likewise be tightened.
Sometimes the reverse process is the issue. Have you ever seen a painting in hot dry weather bow off the wall from excess tension coming into the dry canvas? To ease canvas tension, unwind the screws and tap the corners: the corner retracts back and the tension eases just enough to avoid canvas or timber stress. These days, framers really need to be able to efficiently provide an archival quality product for their customers. An expandable artist stretcher frame, whether the traditional or Belle Arti model, enables you to offer your customers a taut, flat stretched artwork every time, that will continue to look its best in a range of climatic conditions with reassuring ease. It’s all about giving the framer the confidence of complete framing and stretching control.