Wednesday 17 December 2014

What is ...B1 size?

Regular followers of this blog will know that in the middle of the month, I publish a "What is ....? post. The article covers various aspects of paper, printing and finishing in greater depth. However, many of these subjects are complex, so these posts are only intended to be a brief introduction to the topic

What is ...B1 size?
The metric system of sizes which are common in most countries around the world, with the exception of USA and Canada, has been commonplace in the UK since the 1970's. The ISO (International Organization for Standardization) was founded in 1947 and for paper sizes they adopted German DIN (Deutsches Institut für Normung) -  meaning "German institute for standardisation" who established the DIN paper sizes in 1922 .
The whole system of standardisation was so that machinery manufacturers of both printing presses and finishing equipment and suppliers of paper could harmonise production for the benefit of the industry and I think it is fair to say, in comparison with many other industries, it has been a success which, even now, is translating into the new digital/home printing arena.

The premise of the system is to fix the size of finished jobs - being A6, A5, A4, A3 etc. Therefore the system works like this:
'A' sizes are intended to be the finished job sizes
'RA' sizes are to allow grip on the printing press, which is then trimmed to give a finished 'A' size
'SRA' sizes allow for both grip and bleed on the printing area, which is then trimmed to give a finished 'A' size
'B' sizes allow for oversize formats (...whatever that means!)

Here is a list of ISO 'B' sizes - but remember they are 'theoretical' sizes:
B0 1000 x 1414mm
B1 707 x 1000mm
B2 500 x 707mm
B3 353 x 500mm
B4 250 x 353mm
B5 176 x 250mm
B6 125 x 176mm
B7 88 x 125mm

So why this whole post about what size is B1? Well basically it is because it causes much confusion ...and the reason is that  the B1 size held in stock by paper mills and merchants differ from the 'theoretical' B1 size listed above. I have never come across a mill or merchant in the world who holds a B1 sheet size of 707x1000mm in stock - it simply does not exist!

B1 stock sizes can be 720 x 1020mm,720 x 1010mm, 710x1020mm or 700 x 1000mm — all are regarded as B1 size. This can be confusing and is worth considering if you a specifying a particular paper for a project - especially when considering the finished size.

For example, this Modern House brochure which I wrote about on this blog some time ago, is a finished size of 340x240mm. The Omnia used for the text and cover comes in a sheet size of 720x1020mm but the Colorset, Light Grey 120gsm, which also forms part of the text pages, comes in a size of 700x1000mm. Therefore the finished size of the brochure was dictated by the size of the smaller sheet size. If both sheet sizes had been 720x1020mm, it would have been possible to increase the finished size of the job to 345x245mm.
To avoid confusion, either check the B1 stock size of the chosen paper or check with the printer what is the largest size possible out of the sheet size available.

...and one more piece of advice: it's not a good idea to refer to B4 or B5 as "finished job sizes" - T he reason being that you are asking someone to produce a finished size from sheets of paper without allowing any room for trim or bleed, so it is impossible to produce a job to that size - not without doing it either at a ridiculous cost or subsequently reducing the size. If you want to maximise the sheet size (which is an excellent idea) then you are best to give the actual dimensions rather than trying to describe it as a B size job. The Modern House job above (340x240mm) could be described as a B4 size job but I wouldn't advise that because someone may look up the theoretical size (250x353mm, as listed above) and use that size and then you wouldn't then be able to produce the job. Hope that makes sense!

With thanks to Justin at Push for clarifying some of the points in this post.
Posted by Justin Hobson 17.12.2014

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