Composition

Asgehalte 525°C (ISO 1762):

What Determining the weight of ashes of oven-dry paper, expressed in a percentage. At this temperature only paper fibres burn away, most of the fillers, additives and other inorganic materials stay behind as a residue (ash)
Why

Additives like fillers, coating, seizing, OBA have impact on surface characteristics, and therefor on printability, on opacity and certain strength aspects.

How

Oven-dry substrate of 100 cm² is weighed and then ignited in a muffle furnace on 525°C after which the ashes are weighed.

Calculations

Where:
A = weight of ash in g B = weight of oven-dry sample in g Report the average of at least 3 significant measurements.


Ash content 900°C (ISO 2144, TAPPI T413):

What Determining the weight of ashes of oven-dry paper, expressed in a percentage. At this temperature most of the fillers, additives and other inorganic materials also burn, leaving less residue (ash)
Why

Additives like fillers, coating, seizing, OBA have impact on surface characteristics, and therefor on printability, on opacity and certain strength aspects.

How

Oven-dry substrate of 100 cm² is weighed and then ignited in a muffle furnace on 900°C after which the ashes are weighed.

Calculations

Where:
A = weight of ash in g
B = weight of oven-dry sample in g

Report the average of at least 3 significant measurements.


pH-value in cold watery extracts (ISO 6588, TAPPI T509):

What To determine the acidity of the substrate. Values lie between 0 and 14, where values < 7 are considered acidic, 7 is considered neutral and values > 7 are considered alkaline. The pH-value is derived from fibres and all additives present in the substrate.
Why

Acidic free substrates (values of 7.5 and higher) are longer lasting, which is especially relevant for archival storage.

How

Finely cut paper is submerged in distilled water during 4 hours, after which the acidity is determined with a pH-meter, that has been calibrated in a so called buffer fluid that has a pH-value more or less equivalent to the value one is aiming at.

Calculations

Report the average of at least 2 significant measurements.
 

Note

When a substrate should be alkaline the lower limit of pH 7.5 is applied.
When testing specific artist’s material, the pH-value may not be lower than the target value minus 0.5.
 

Fibre composition using Herzberg stain (ISO 9184-3, TAPPI T401):

What To determine the main fibre content of a substrate framed in a slide by colouring the obtained fibres with Herzberg stain (a saturated solution of zinc chloride, iodine and potassium iodide in distilled water.)
Woody fibres will react differently to this indicator than e.g. cotton or linen (colourisation)
Why

For certain applications it may be of interest to know what fibres are used or how much of a specific fibre a substrate contains (e.g. passports or banknotes)

How

A very small piece of the paper is dissolved in distilled water and after it is left to dry to the air, a drop of stain is added and the solution is framed in a slide. Evaluation takes place under a microscope. Count all fibres present, record woody fibres and other (e.g. cotton) separately.
Microscopic picture is possible.

Calculations

Report the average presence of wanted fibres of at least 2 specimens expressed as a percentage.


Detecting woody elements with floroglucinol solution (TAPPI T401):

What To determine the presence of wood (lignin) in paper and board.
Why

Wood gives thickness and bulk and therefor generates opacity and stiffness. Up to a certain degree, lignin is a cause of yellowing (ageing) of paper.

How

A piece of paper is torn and on the fibrous edge a drop of floroglucinol is applied. Woody elements will react by colourisation from pinkish to deep purple red.

Report by means of a microscopic picture.

Note

Also wood free paper may contain a certain amount of woody elements. At a ratio of 70% cellulose and 30% wood pulp the cellulose may be partly replaced by CTMP (Chemical Thermal Mechanical Pulp) from which lignin is not removed but encapsulated.


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