Use of carbon papers or carbon coatings
The method to be adopted for making such copies of the form as are required in use must be carefully considered since it may substantially affect certain aspects of its design. The methods principally used are described below.
Use of carbon papers or carbon coatings
Various grades of paper and carbon paper, suitable for different methods of entry and yielding different numbers of copies are obtainable. For good results it is important to ensure that the right kind of carbon paper is used with a suitable paper, both when trying out new ideas and for the finished forms. Slight differences in the performance of carbon papers may occur from time to time, and it may be necessary to make some allowance for these unavoidable manufacturing variations. When necessary H.M. Stationery Office should be consulted on special technical points about the matching of suitable papers for copying purposes.
The main groups into which carbon papers can be divided are:
- Pencil carbons, one or two-sided
- Pen carbons
- Typewriter carbons
- Hectographic and spirit duplicator carbons
- One-time carbons, either as separate sheets, or as carbonised forms; these are used for handwriting and for typewriting etc.
Carbon papers in Groups (1)-(4) above are stocked by H.M. Stationery Office, but any requirements in Group (5) are purchased specially. Two-sided typewriter carbons, carbons of special high quality, carbons for use with addressing plates, and supplies such as paper-edged carbon to facilitate handling and insertion in sets of forms, also need to be specially purchased for departments.
Coloured carbons are obtainable as follows, but the colours shown in brackets are not normally stocked by H.M. Stationery Office:
- Pencil carbons: black, blue (purple, red, green)
- Pen carbons: blue (black)
- Typewriter carbons: black (blue, red, yellow, green)
- Hectograph and spirit duplicator carbons: purple, red, green, black (blue, brown)
Black carbons with a red strip for use on accounting documents are also obtainable, but cost more than one-colour carbons and need to be specially purchased.
For writing and typewriting the colours black purple and blue give the best legibility on white or buff paper. Black should be absolutely permanent; blue and purple are reasonably resistant to fading; but the green and red, although retaining their colour for a considerable time, will eventually fade, and are not therefore suitable when permanency is an essential feature.
For hectograph and spirit duplicators, the colour normally used is purple on account of the high tinctorial strength of the dye used; of the other colours available none is at present equal to purple in depth, but improvements are continually being made.
Pencil carbons are designed for use with a fairly hard pencil, and it is advisable to use a backing sheet of card or metal if more than one carbon copy is to be taken.
Two-sided pencil carbons are designed for use with manifold books or sets— when the top or second copy is on tissue or translucent paper, the carbon entry on the back of the tissue paper being read through this paper; thus one sheet of two-sided carbon paper can be used to produce three copies (a top copy, the tissue copy, and a copy underneath the two-sided carbon). In another application of this type of carbon the impression on both sides of a sheet makes alteration or falsification more difficult. Two-sided carbon paper is about 25% more expensive than one-sided carbon and the latter is preferable unless the copying methods offer a compensating saving by the use of two-sided carbon and tissue paper.
Pen carbons are more sensitive than pencil carbons, and a backing sheet or plate is generally necessary. Sensitive carbons reproduce pressure marks upon the top copy with fingers as dirty marks on the carbon copies, but such blemishes can be avoided.
Ball pens are the most efficient writing instruments for use with either pencil or pen carbons but their use also involves more rapid exhaustion of the carbon paper. For pen carbons, specially hard manifolding pens are available; ‘S.O. No. 12 Manifold Pen’ (Code No. 50-66) is the most suitable for producing copies from pen carbons.
Typewriter carbons are stocked by H.M. Stationery Office, in two weights but only one colour (black), as follows:
- Light, which will give up to 8 copies at one time on normal weights of paper.
- Extra light, which will give up to 15 copies at one time on thin paper.
The number of carbon copies obtainable with a typewriter will depend on:
- The weight and quality of the stationery used.
- The make, age, state of repair and cleanliness of the machine used.
- The hardness and condition of the typewriter platen.
- The touch of the operator.
There is a limit to the total thickness of paper which may be passed into a typewriter and good copies cannot be produced if too many sheets of paper are used.
A more sensitive carbon paper will be needed for machines with a softer stroke. The number of carbon copies, obtainable therefore varies up to about eight copies with an ordinary typewriter, to perhaps 20 with an electric typewriter. Carbon copies can be made through cards on an Underwood Elliot Fisher flat-bed machine.
When it is intended to obtain copies on papers of other than ‘standard’ weights and
|Purpose for which intended|
|Pencil, blue||7 × 8¾||2–63||To take a maximum of three copies of the top copy with a copying ink pencil or ball pen|
|Pencil, blue||8 × 13||2–64|
|Pencil, blue||6½ × 11||2–65|
|Pencil, blue||8 × 11||2–69|
|Pen, blue, extra sensitive||7 × 8¾||2–73||For use with a thin top copy, pen being used; the duplicate being suitable for record purposes and for sending out|
|Pen, blue, extra sensitive||8 × 13||2–74|
|Pen, blue, extra sensitive||8⅝ × 15¾||2–78|
|Pen, blue, extra sensitive||15½ × 19||2–76|
|Type, black, light weight||4⅜ × 7||2–21||To take up to eight copies at one time on thin typewriting paper|
|Type, black, light weight||6½ × 8||2–22|
|Type, black, light weight||7 × 8¾||2–223|
|Type, black, light weight||8 × 13||2–224|
|Type, black, light weight||13 × 16||2–25|
|Type, black, light weight||5⅞ × 8¼ (A5)||2–225|
|Type, black, light weight||8¼ × 11¾ (A4)||2–226|
|Type, black, extra light weight||6½ × 8||2–29||For use when up to a maximum of 15 copies on thin paper are required at one typing|
|Type, black, extra light weight||8 × 13||2–30|
|Type, black, extra light weight||5⅞ × 8¼ (A5)||2–228|
|Type, black, extra light weight||8¼ × 11¾ (A4)||2–229|
|Spirit duplicator, purple, red, green, black||7 × 8¾||*||For use with spirit duplicator. See H.M.S.O. Guide: Part 1|
|8 × 13||*|
|13 × 16||*|
* These sizes are available for each colour; see H.M.S.O. List of Paper and Office Requisites held in stock for use in the Public Service.
Carbon papers other than those shown above need to be specially purchased by H.M. Stationery Office for departments. qualities it is necessary to experiment with various papers, carbons and platens to obtain optimum results.
One-time carbons. A very thin and lightly-coated sheet of carbon paper may be interleaved with sets of forms (whether used in pad form or with a machine). Coloured one-time carbon paper is available. For the same number of operations one-time carbon paper costs more than ordinary carbon paper and the question is whether the extra costs are justified by increased output.
No carbon required (NCR) paper is chemically treated to produce copies without interleaving carbon sheets. It is dearer than comparable quality paper plus carbon: so much so that, for very large quantities, carbon bonding or patching may be cheaper. Patch coated NCR paper is not yet available although small areas can be desensitised by the printer. Six good copies can be obtained with a ball pen, but a hard writing surface is required. Up to eight copies can be obtained with a standard typewriter, and twelve or more copies with an electric typewriter. Copies are as good as those produced by blue carbon. The coating is sensitive and subject to accidental pressure marks. Errors cannot be corrected by erasure. NCR paper can be used for Continuous Stationery. Three kinds are made—for top, intermediate and bottom copies respectively.
The carbon-coated type of form can be used when ordinary carbon paper is not suitable for making manifold entries, for example when it is necessary to avoid interleaving with separate sheets of carbon paper or when certain entries only are required.
Production facilities for carbon-coated forms are limited because only a few manufacturers undertake this work. They are about two-thirds more costly than forms used with ordinary carbon even when relatively large quantities are ordered. For smaller quantities, i.e. 50,000, the cost may be as much as three times the cost of an ordinary form. Accordingly H.M. Stationery Office normally require evidence of savings in staff time etc. gained by using this kind of stationery in preference to ordinary forms and carbon paper. Small quantities can sometimes be obtained for a trial run.
The carbon coating can be applied either as part of the printing process, when it resembles printing ink, or as a separate operation, when it gives a coating similar to that used for normal one-time carbons. The latter gives by far the better impression, and is generally preferred because the ‘printed’ variety is liable to dry out and become ineffective after comparatively short storage.
Coloured coatings are available; blue and purple are satisfactory, but red and green may be fugitive in strong light.
The carbon coating can be laid on the form in two ways:
In bands in which the carbon coating is flowed on to the paper in continuous bands along the whole length of the reel of paper. Bands can be varied in width and position, the reel being cut subsequently into separate sheets on which the bands of carbon run from edge to edge. Band carbonised forms are usually printed after carbonising.
In patches: with this process the carbon coating is ‘printed’ from special blocks of the required size or shape using liquid carbon coating instead of printer’s ink. The face sides of the forms are usually printed prior to carbonising.
The edges of the coating must register with the entry spaces on the face of the form.
Patch coating is more expensive than band coating; and the production facilities for patch coating are even more limited than those for band coating. For these reasons patch carbonising should be avoided as much as possible, by designing the form in such a way that bands of carbon coating pass under the appropriate entry spaces; if by this method the carbon coating extends under entries which should not appear on the copies of the form, it may be practical to obscure the unwanted carbon entries on the copies by printers’ ornaments, or heavy black shading.
The main advantages of carbon-coated forms are:
- Greater convenience in handling.
- Selective copying is possible thus freeing space on the under-copy or enabling the size to be reduced.
The main disadvantages of carbon-coated forms are their greater cost and limited production facilities. Other less important disadvantages include:
- The paper used is limited to that suitable for carbon coating.
- Some recipients of forms do not like carbon coating. The carbon coating may rub off and soil the hands, or adjacent papers in files.
- The carbon coating tends to soak through the paper, darkening the writing surface, and reducing the legibility of pencil entries on the carbon-coated form.
- Alteration and correction can be made only by crossing out and re-writing.
- Carbon-coated forms are not good salvage.
In view of the difficulties associated with the supply of carbon-coated forms, early consultation with H.M. Stationery Office is advisable, after other and possibly more economical methods of making copies of entries have been studied.
Registration of entries made by carbon
When entries are made simultaneously on more than one copy of the form (e.g. a four part carbon set), some inaccuracy in registration may be caused by the bulk of carbon interleaved between sheets, or by a typewriter platen slipping. If tolerance is not allowed in fixing the size of the entry spaces, entries on the under copies may encroach on printed lines or even on adjoining entry spaces.
The accuracy of registration depends partly on the device used to hold the forms together during the entry process. Registration is usually more difficult to maintain with large forms unless special devices are used.
The following methods may be used to facilitate registration:
- Providing deeper or larger entry spaces on the under copies or dispensing with lines and boxes for some parts of the form.
- Ruling heavy lines to help the eye when aligning forms of different size.
- Stapling or padding sets of forms.
- Using holding devices such as peg boards, or a folded card, to align and hold documents in position during the writing of entries. (The registration and the feed of multi-part forms used in some accounting machines, teleprinters, or with hand registers, can be controlled by sprocket devices engaging in a series of holes punched in the margins of the form.)