Question Why need to gap center stretch bar in frame?

[cheonmu]

Hi,

I am buying stretcher bar frame from supplier and using that for wrapping canvas wrap.

But strectcher bar maded by supplier, alwasy has gap between stretch bar.

why need to gap center stretch bar in frame?

Are there any standards as to how far apart that should be?

 

[artfolio]

Stretcher bars usually have sliding joints in the corners and the centre bar is fitted a little bit loosely. There are also usually slots in the corners where wedges can be driven in to add tension and square the frame after the canvas has been stretched.

It is best to ensure the frame is perfectly square before you start stretching the canvas and I used to pin the corners temporarily while doing this as it is easy to pull it out of square. Many ready-made stretchers are of poor quality and it is advisable to check them over thoroughly for warped or twisted sides.

Your illustration shows square cut sides and I hope that your stretcher actually has the face sloped downwards towards the centre and the outside edge rounded as sharp corners will damage the canvas and the inner edge will raise an ugly line in the artwork after a few days.

 

[Jim Miller]

Welcome to The G, Cheonmu.

The canvas should contact the stretcher frame (or strainer frame - they are different) with minimal area and only at the edges. That is why the profile of the moulding used for canvas supports has a raised lip on the outside edge. Like this:



If the canvas were stretched over a frame built out of moulding without that raised lip, then deformation of the canvas surface and cracks would eventually develop in the painted image at the inside edges of the moulding. Likewise, if an internal reinforcement were in direct contact with the back of the canvas, it would cause cracks in the paint over time.

Like this:


Or this...



For more on this topic and other information about framing canvas artworks, refer to the PPFA Guidelines for Framing Works of Art on Canvas, or Paul MacFarland's Framing Works of Art on Canvas. Both of these excellent texts are available from the PFM and PPFA Bookstores.

 

[JFeig]

Your image is showing a "strainer" with a center reinforcement bar. The 2 parts are not normally made from the same wood moulding. The strainer stock has a raised outer lip to keep the stretched fabric off of the bars (as the photo from Jim Miller that shows the resulting damage). The center reinforcement moulding stock is thinner (without the raised lip) so as to not touch the fabric.

With a strainer - this center reinforcement is touching the strainer stock. This keeps the opposite sides from sagging inwards.

With a fully adjustable stretcher system, the center reinforcement bar has a "mortice and tenion" connection that allows for expansion and contraction.

 

[Shayla]

Hi, Cheonmu. Welcome to the Grumble!

Is the center reinforcement bar physically attached to the rest of the stretcher frame, or does it just slide into pre-cut holes in the stretcher? From your note, it sounds like it might slide loosely, and that when you have it assembled, the bar slides out of the hole a bit, leaving a gap. Is this correct, or is the gap you mention something different? Also, when you measure the assembled stretcher frame, is the width across the center (in the same direction as the reinforcement bar), the same as the width at both ends of the stretcher frame? I am also curious as to what size your frame is. A few years ago, we stretched a 7 x 10 foot (2 x 3 meter) canvas, and the center bar needed some adjusting. It had loose 'sliding' reinforcement bars, and when assembled, it was narrower across the center than on the ends. That was better than if it had bowed out too wide, but it was still a problem. In our case, it came with extra plastic attachments, and we were able to add shims between those and the stretcher frame to make it even. Then, it looked good in the float frame.

Thank you for taking time to read my note, and we wish you success!

 

[cheonmu]

Welcome to The G, Cheonmu.

The canvas should contact the stretcher frame (or strainer frame - they are different) with minimal area and only at the edges. That is why the profile of the moulding used for canvas supports has a raised lip on the outside edge. Like this:
View attachment 40795


If the canvas were stretched over a frame built out of moulding without that raised lip, then deformation of the canvas surface and cracks would eventually develop in the painted image at the inside edges of the moulding. Likewise, if an internal reinforcement were in direct contact with the back of the canvas, it would cause cracks in the paint over time.

Like this:
View attachment 40793

Or this...

View attachment 40794

For more on this topic and other information about framing canvas artworks, refer to the PPFA Guidelines for Framing Works of Art on Canvas, or Paul MacFarland's Framing Works of Art on Canvas. Both of these excellent texts are available from the PFM and PPFA Bookstores.

Hi, Jim Miller

hanks for your detailed answer.

I have same art like you uploaded.

I know the problem is Frame but i was not sure what is reason correlty.

If, frame must attach with canvas to minimum area, is there any standard for width of frame bar?

And i saw book as you linked but unfortunally, books are not supported as E-book.

S.Korea do not have Amazon, so i will find to way to ship book to Korea.

Thank you and Happy new year!

 

[cheonmu]

Hi, Cheonmu. Welcome to the Grumble!

Is the center reinforcement bar physically attached to the rest of the stretcher frame, or does it just slide into pre-cut holes in the stretcher? From your note, it sounds like it might slide loosely, and that when you have it assembled, the bar slides out of the hole a bit, leaving a gap. Is this correct, or is the gap you mention something different? Also, when you measure the assembled stretcher frame, is the width across the center (in the same direction as the reinforcement bar), the same as the width at both ends of the stretcher frame? I am also curious as to what size your frame is. A few years ago, we stretched a 7 x 10 foot (2 x 3 meter) canvas, and the center bar needed some adjusting. It had loose 'sliding' reinforcement bars, and when assembled, it was narrower across the center than on the ends. That was better than if it had bowed out too wide, but it was still a problem. In our case, it came with extra plastic attachments, and we were able to add shims between those and the stretcher frame to make it even. Then, it looked good in the float frame.

Thank you for taking time to read my note, and we wish you success!

Hi, Shayla

Thanks for your detailed answer!

Center bar is attached physically and fixed by Nail gun.

And this frame is not a "Normal frame" you think.

This frame is made by Meranti wood stick and size is 2,8cm(1.1") x 2.8cm(1.1") and There is a slight rounded.

Frame size is 31" x 26".

Usually, we uses this wood when buliding or interior as Frame in S.Korea.

I'm currently getting these frames from vendors, but I'm trying to make a slightly better frame myself.

I never saw Plastic center bar before, Thanks for letting me know that there is a new way.

And happy new year!

 

[cheonmu]

이미지에 중앙 보강 바가 있는 "스트레이너"가 표시됩니다. 2개의 부품은 일반적으로 동일한 목재 몰딩으로 만들어지지 않습니다. 스트레이너 스톡에는 늘어난 천이 막대에서 떨어지지 않도록 외부 립이 돌출되어 있습니다(결과 손상을 보여주는 Jim Miller의 사진 참조). 센터 보강 몰딩 스톡은 천에 닿지 않도록 더 얇습니다(돌출 립 제외).

스트레이너 사용 - 이 중앙 보강재가 스트레이너 스톡에 닿아 있습니다. 이렇게 하면 반대쪽이 안쪽으로 처지는 것을 방지할 수 있습니다.

완전히 조정 가능한 들것 시스템과 함께 중앙 보강 바에는 팽창 및 수축을 허용하는 "장붓구멍과 장력" 연결부가 있습니다.

Hi, JFeig

I've bought many frames from vendor, but this is the first time I've seen about Strainer.

The art is not general(universal) product from South Korea.

It's very hard to find a framer, and there is absolutely no information about making a frame.

Thanks for answering my question and Best wishes for a Happy New Year!

 

[JFeig]

As an alternative idea for you needs, you might look into the home construction industry for a company that manufactures pre-milled decorative moulding trim for doors and windows. They use 4 or more side industrial moulding machines that you do not have an affordable access to. As an example:

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With such a machine, there are standard premade cutting knives available as well as custom knives.

 

[Shayla]

Hi, Shayla

Thanks for your detailed answer!

Center bar is attached physically and fixed by Nail gun.

And this frame is not a "Normal frame" you think.

This frame is made by Meranti wood stick and size is 2,8cm(1.1") x 2.8cm(1.1") and There is a slight rounded.

Frame size is 31" x 26".

Usually, we uses this wood when buliding or interior as Frame in S.Korea.

I'm currently getting these frames from vendors, but I'm trying to make a slightly better frame myself.

I never saw Plastic center bar before, Thanks for letting me know that there is a new way.

And happy new year!

Hi, cheonmu. Thank you for your reply. I should clarify that the center bar was not plastic. The plastic part was an adjustable attachment that helped attach the center bar to the outside of the frame. I know that this is not the same as what you have, but you still might find this helpful to see. Our large frame was from this company, and the plastic parts I mentioned are called 'Best Brace Bracket'. The thing that you might find most helpful from their site is, the diagram that shows how many bracer bars to use for what size frame. That diagram is the last image in the second link. https://products.richesonart.com/collections/stretching Stretcher Bars & Accessories

https://www.richesonart.com/pdfs/framingguide.pdf

 

[Nikodeumus]

As an alternative idea for you needs, you might look into the home construction industry for a company that manufactures pre-milled decorative moulding trim for doors and windows. They use 4 or more side industrial moulding machines that you do not have an affordable access to. As an example:

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies

With such a machine, there are standard premade cutting knives available as well as custom knives.

Dear Santa.....I WANT THIS!!!

 

[cheonmu]

Hi, cheonmu. Thank you for your reply. I should clarify that the center bar was not plastic. The plastic part was an adjustable attachment that helped attach the center bar to the outside of the frame. I know that this is not the same as what you have, but you still might find this helpful to see. Our large frame was from this company, and the plastic parts I mentioned are called 'Best Brace Bracket'. The thing that you might find most helpful from their site is, the diagram that shows how many bracer bars to use for what size frame. That diagram is the last image in the second link. https://products.richesonart.com/collections/stretching Stretcher Bars & Accessories

http://[URL]https://www.richesonart.com/pdfs/framingguide.pdf

[/URL]

Hello, Shayla

Thanks for answering.

I missunderstood. my english skill is not a good XD

I saw you linked PDF file and i understand correclty what you says now.

I didn't know there were so many methods and parts for making a frame or canvas.

Even at most largest company (provider) that sells the frame in Korea, there is registered only one type of canvas stretcher bar.

Thank you so much for letting me to know. I'm still just a beginner, but I'll try to make a better frame than used now.

 

[cheonmu]

As an alternative idea for you needs, you might look into the home construction industry for a company that manufactures pre-milled decorative moulding trim for doors and windows. They use 4 or more side industrial moulding machines that you do not have an affordable access to. As an example:

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies

With such a machine, there are standard premade cutting knives available as well as custom knives.

It's a great machine. I really wish I had one of those machines.

But it's not possible to buy in Korea, and it looks very expensive XD

Thanks so much for letting me know though!

 

[JFeig]

I agree that it is an expensive machine. That is why I suggested that you fine someone else with a machine of similar function and the purchase moulding made from this machine, only as much as you need, verses buying the machine.

 

[Shayla]

Hello, Shayla

Thanks for answering.

I missunderstood. my english skill is not a good XD

I saw you linked PDF file and i understand correclty what you says now.

I didn't know there were so many methods and parts for making a frame or canvas.

Even at most largest company (provider) that sells the frame in Korea, there is registered only one type of canvas stretcher bar.

Thank you so much for letting me to know. I'm still just a beginner, but I'll try to make a better frame than used now.

Hi, Cheonmu. Yes, I was also surprised at the wide variety of stretcher frames available. When we have bought these from this company, they have been wonderful. We also make strainer frames for smaller projects, which are different from stretcher. Stretchers have adjustable corners, but strainer frames have fixed corners, with the wood legs being joined permanently and non-adjustable. We use moulding for this that has an extra, rounded top edge, so that, as the first two writers said, it holds the canvas above the stretcher frame wood. We have also begun to do something the Rob Markoff suggests, which is to stretch the canvas the day before and hold it in place with metal tacks. Then, the next day, we remove the tacks on three sides and re-stretch and staple the canvas. This helps the canvas to relax a bit before stretching, so that it is less likely to relax afterward.

 

[Jim Miller]

...If, frame must attach with canvas to minimum area, is there any standard for width of frame bar?

As far as I know, there is no clear standard for widths of strainer or stretcher moulding profiles. The main concern is to use a moulding that is strong enough to resist warping, bending, or deflection under tension of the stretched canvas. This could involve a wide, shallow profile, or perhaps a narrower, deep profile. And if the selection of moulding profile is suspected to be weak, then reinforcing bars should be included.

The tension of stretching the canvas is important, too. Opinions differ, but friendly conservators have told me that the canvas should be stretched only as much as necessary to keep it perfectly flat. If the canvas relaxes over time and shows wrinkles, then it can be re-tensioned by keying out the corners of the stretcher frame.

Since keying-out is not possible with a strainer frame, you may want to apply a little more tension. In any case, avoid making the canvas so tight that the paint cracks. Also, if too tight, the canvas could shred if it were to shrink for any reason.

 

[Prospero]

Harking back to Jim Miller's post ☝️ up there, I have seen that happen with many canvases in my time and as
it happens I have one at the moment with I am remounting on 'proper' bars. I have just this morning managed to
get it off the bars.
I was a bit bemused as to why it it happened because the bars were keyed and why there was no lip on the bars.
It transpired when I looked closer at the bare frame that the bars were bevelled, but whoever stretched the blank
canvas (it was a DIY job) put it on the back, square face, of the bars which was flat. That's artists for ya. 🙄

I'm hoping the dent will relax out, but I am not too hopeful.