Knowledge Base
Recycled Fiber Contaminants: Key Terms & Standards
A reference glossary for quality engineers, lab technicians, and sustainability professionals working with recycled pulp and recovered paper furnishes. For hands-on testing instruments that measure these contaminants, see the Pulmac MasterScreen™ and the full paper and pulp testing equipment range from Industrial Physics.
Stickies
Tacky or adhesive contaminants in recycled pulp, originating from pressure-sensitive adhesives, hot melts, wax coatings, and latex binders. Classified as macro stickies (greater than 150 µm – measurable by laboratory screening) or micro stickies (less than 150 µm – depositing on machine clothing). Measured using the Pulmac MasterScreen™.
Shives
Incompletely pulped fiber bundles released during pulping or refining. Shives appear as distinct fiber clusters in the pulp slurry and cause surface defects and sheet uniformity issues. Tested per TAPPI T 275 using instruments such as the TMI Büchel Somerville Screen, or per TAPPI T 274 using the MasterScreen™.
Vessel cell elements
Anatomical fragments of hardwood fibers (e.g., eucalyptus, birch) released during pulping. In fine papers, vessel cell elements cause “vessel picking” defects during printing.
DIP – Deinked Pulp
Recycled pulp produced from printed wastepaper through a deinking process. Used in tissue, newsprint, and fine paper grades. Stickies analysis in DIP is governed by INGEDE Method 4.
OCC – Old Corrugated Containers
One of the most widely used recovered paper grades, consisting of used corrugated boxes. OCC introduces hot melt adhesives and wax contamination into the recycled fiber stream.
MOW – Mixed Office Waste
A recovered paper grade consisting of a mix of office papers. MOW typically carries higher loadings of pressure-sensitive adhesive stickies from labels and sticky notes.
Low consistency screening
A pulp screening process conducted at dilute slurry consistency (typically 0.1-0.5% fiber). The Pulmac MasterScreen™ operates on this principle, passing fibers through a precision screen while retaining contaminants.
AutoFilter
A component of the Pulmac MasterScreen™ that automatically deposits retained contaminants onto a filter paper at the end of a screening run, enabling rapid visual or image-based analysis.
Macro stickies
Stickies particles large enough to be retained and quantified by laboratory screening equipment. Measured per TAPPI T 277 pm-99, INGEDE Method 4, and ASTM D6148.
Freeness
A measure of how quickly water drains from a dilute pulp suspension, used to monitor the effect of beating and refining on fiber drainage behavior. Tested using instruments such as the Schopper-Riegler Freeness Tester or the Canadian Standard Freeness Tester. See also: freeness testing of pulp mixtures.
Screen plate aperture
The slot or hole size in the precision screen used during pulp screening. The MasterScreen™ uses laser-cut screen plates in standard sizes of 0.004″ and 0.006″, with custom sizes available from 0.003″ to 0.014″.
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FAQs
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Stickies are tacky contaminants in recycled pulp that originate from pressure-sensitive adhesives, hot melts, wax coatings, and synthetic polymers present in the recovered paper stream. They cause machine downtime by accumulating on screens, felts, and press rolls, and create surface defects – blemishes, picking, and coating failures – in the finished paper or board product. Managing stickies is a core quality challenge for any mill using recycled fiber, particularly those processing deinked pulp (DIP), old corrugated containers (OCC), or mixed office waste (MOW). The Pulmac MasterScreen™ is the standard instrument used to measure and quantify macro stickies in the laboratory.
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The Pulmac MasterScreen™ is a low consistency screening device that mechanically separates fibers from contaminants by passing a dilute pulp slurry through precision laser-cut screen plates at controlled pressure (up to 15 PSI). Fibers pass through the screen apertures; contaminants – stickies, shives, dirt, vessel cell elements, plastics, and hot melts – are retained. The AutoFilter system then automatically deposits these retained contaminants onto a filter paper for analysis. Results are available in 10-15 minutes. Standard screen plate apertures are 0.004″ and 0.006″, with custom sizes available between 0.003″ and 0.014″. It is part of the Technidyne brand portfolio, available through Industrial Physics.
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The primary standards for laboratory pulp screening and stickies measurement are: TAPPI T 274 sp04 (Laboratory Screening of Pulp using a MasterScreen-type instrument), INGEDE Method 4 (Analysis of Macro Stickies in Deinked Pulp), ISO 15360-2:2001 (Recycled Pulps: Estimation of Stickies and Plastics by image analysis), TAPPI T 277 pm-99 (Macro Stickies Content in Pulp: The Pick-Up Method), and PAPTAC C.12P (Laboratory Screening of Pulp using a Pulmac-Type Instrument). For shive analysis, see also TAPPI T 275, which is supported by Industrial Physics through the TMI Büchel Somerville Screen.
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Macro stickies are particles typically larger than 150 micrometers (µm) that are retained by laboratory screening equipment and can be directly collected, counted, and weighed. They are the form of stickies measured by instruments like the Pulmac MasterScreen™ under standards such as TAPPI T 277 and INGEDE Method 4. Micro stickies are particles smaller than ~150 μm that pass through standard screens and deposit on paper machine clothing – felts, wires, and rolls – causing wire and felt blinding and surface quality issues that are harder to trace to a single contaminant source. A high macro stickies count is often a reliable indicator of elevated micro stickies risk.
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As recycled fiber use increases in response to sustainability legislation and brand owner targets – including EU Packaging and Packaging Waste Regulation (PPWR) recycled content requirements – contamination control becomes more critical, not less. Regular laboratory pulp screening with instruments like the Pulmac MasterScreen™ provides the data needed to demonstrate that recycled furnishes meet quality specifications, validate the performance of cleaning and screening stages in the process, reduce reject rates and resource waste, and support compliance with sustainability certifications. For a complete picture of pulp quality testing – from contamination screening to freeness, strength, and optical properties – explore the full paper and pulp testing range from Industrial Physics, or contact our team to discuss your requirements.
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