Paper and Grain · FIELD NOTE 13
Sizing in Paper: Why a Sheet Takes Ink Differently
What does paper sizing change?
Two papers that feel equally smooth can respond very differently to a written line. On one, ink may remain crisp; on another, it can spread into a soft edge. Fibre, formation, surface, and the ink itself all matter, but sizing is one important part of the explanation. Understanding its purpose helps a maker choose and test new stock. It does not justify putting water or ink on a historic sheet merely to discover how that sheet was made.
Sizing changes an interaction
In paper terminology, sizing concerns resistance to liquid penetration and related surface properties. Roberts and Etherington distinguish internal and surface sizing and describe effects beyond simple absorbency, including surface strength and handling characteristics. It is therefore misleading to define sizing only as a glossy coating. The relevant question is what interaction the treatment was intended to control: liquid entering the sheet, fibres lifting at the surface, or a combination of properties needed in use. [1]
CAMEO lists several material families associated with sizing, including gelatin, starch, gums, and synthetic materials. The range matters because size is not one substance with one universally predictable response. Nor is the material's presence established by a smooth or shiny appearance alone. A manufacturer's description may identify a treatment in new stock, whereas visual examination of an old leaf may only reveal features consistent with several possible preparations. [2]
Internal and surface descriptions answer different questions
Internal sizing is introduced during paper manufacture within the furnish, while surface treatment is applied to the sheet. For an introductory comparison, imagine controlling access through a network versus treating its outer boundary. This is an explanatory analogy, not a microscopic description of every paper. Actual distribution and effect depend on materials and manufacturing. It helps explain why two papers described as sized need not behave alike when a maker applies a wash or writes a fine line.
A label such as drawing paper or writing paper can also conceal variation. The intended medium might require a surface that permits a sharp line, accepts a controlled wash, withstands erasure, or combines several of these demands. Do not rank papers by most sizing as though more were always preferable. Specify the action the paper must support first. A wet-media study and a folded reading booklet can make quite different demands on the same sheet.
Build a relevant sample comparison
For a new project, take expendable samples from candidate stocks and use the actual intended pen, ink, or paint. Keep the application comparable and label each sample before working. Record what you observe: edge spread, drying behavior, show-through, surface disturbance, or difficulty folding after the sample dries. This is a proposed practical exercise, not a set of published test results. It evaluates suitability for a task rather than identifying an unknown sizing recipe.
Avoid interpreting one mark too quickly. A broad line may reflect the amount of ink delivered, pressure, application method, or the medium as well as the paper. If the first result is surprising, repeat on another sample with a controlled change. Changing paper, ink, nib, and technique together makes the comparison difficult to read. A small, labelled series usually gives a maker better evidence than an unrecorded trial on the final page.
Do not confuse sizing with a repair adhesive
Some material names appear in both papermaking and conservation. That overlap does not mean that applying a household version to an old page restores its original surface. The treatment would introduce moisture and material, and it could affect media or later examination. A technical term can explain a property without authorizing a procedure. Recreating a historical recipe is also different from choosing an appropriate treatment for a particular aged object.
If a sheet shows uneven penetration, tide marks, or a rubbed patch, describe those features without declaring that sizing has failed. A repair, earlier washing, an intentional working process, or local handling may be relevant, but the history may be unknown. Record where the appearance changes and whether the medium is stable enough for consultation. The immediate need may be supported access rather than restoration of a presumed original surface.
Folding introduces another criterion
A paper that accepts a beautiful line may still resist the format of a small folded book. Make a separate structural dummy with the proposed stock, because the medium sample and the folding sample answer different questions. Include the intended number of nested sheets and the planned cover relationship. This prevents a successful ink test from being mistaken for approval of the entire binding. Paper selection belongs to the complete object, not one attractive sample mark.
Keep a useful selection record: product name, known sizing information, chosen medium, observed response, and any unresolved limitation. If another batch is purchased, repeat the task-specific comparison where important. The record need not claim laboratory precision to be valuable. It simply allows the next decision to begin with identifiable evidence rather than a remembered impression that one paper once felt better under a pen.
Sizing is most useful as an explanation of controlled interaction. It helps connect material preparation with the behavior a maker actually needs, while leaving room for other causes of a visible result. Test expendable stock, distinguish a product description from an identification, and keep historic objects outside the experiment. The reward is a more informed choice of paper without converting curiosity about absorbency into an unnecessary intervention.
Sources
References below support the factual explanations in this article. Read each source within its stated scope and context.