Pitch, stickies, scale and slime are quietly eroding productivity — costing packaging and tissue machines the equivalent of 4% of their daily output. A holistic program blending smarter chemistry, cleaner loops and sharper raw‑material choices is changing that.
Production losses and runnability impacts
Deposits of pitch (wood resins), stickies (adhesives from recycled paper), scale and biological slime can severely disrupt paper production. Even a small buildup on wires, felts or dryers causes sheet breaks, holes, quality defects and unplanned downtime (link.springer.com) (www.degruyterbrill.com).
One industry report notes that packaging and tissue machines “lose the equivalent of 4% of their output per day due to machine contamination and sheet breaks caused by deposits” (www.cleanroomtechnology.com). Unchecked slime and biofilms spoil raw materials, corrode equipment and emit odorous gases (www.degruyterbrill.com).
It’s why deposits are “one of the most important factors limiting the productivity on a paper machine” (link.springer.com). The risk is rising as recycling grows: around 38% of global fiber supply comes from recovered paper, which greatly increases stickies and foam problems. Robust deposit control is economically critical.
Deposit categories and material origins
Organic pitch and stickies (insoluble, tacky particles) originate from wood extractives or recycled paper; their agglomeration and adhesion to equipment are persistent challenges (www.cleanroomtechnology.com). Scale (e.g., calcium carbonate, sulfate salts) precipitates when soft water is evaporated or heated, especially in evaporators and dryers. Microbial slime — biofilms of bacteria, yeast and fungi — proliferates where residual starches and sugars are present, clogging lines and spoiling sheets.
As one review stresses, trees are “living material” rich in extractives, and recycled pulps contain many nonsoluble contaminants that “cause a deposit problem” throughout the papermaking system (link.springer.com). In practice, mills contend with mixed deposits across wires, felts, rolls and tanks, so control programs must address insolubles, tacky fines and microbes simultaneously.
Chemical treatment programs and dosing control
Two application modes dominate: surface cleaning (sprayed cleaning showers or boil-outs) to remove localized buildup on felts, rolls or wires, and internal additives that circulate with the wet stock so deposits never agglomerate (www.jstage.jst.go.jp).
Dispersants — often water‑soluble polymers or surfactants — bind hydrophobic pitch/sticky particles and keep them dispersed. Archroma reports that its new anionic polymer (Cartaspers PLH) “attracts non-polar (hydrophobic) substances like stickies and natural pitch,” passivates them and “prevents agglomeration and deposition,” without reacting with cellulose (www.cleanroomtechnology.com). In contrast with inert minerals like talc, modern dispersants do not add ash or scale — Cartaspers “does not cause scale deposits in evaporators or contribute to ash content” (www.cleanroomtechnology.com). An effective dispersant program can maintain runnability and sheet cleanliness while cutting chemical and cleaning costs.
Trials at two pulp mills found that using a single polymeric dispersant (instead of three older products) gave “better performance in soft water and significant cost savings” (www.cleanroomtechnology.com). Detackifiers — typically cationic or weakly cationic polymers — neutralize tacky extractives and adhesives, masking charges so contaminants lose stickiness. For recycled stock, detackifiers (e.g., modified starches, polyamines or specialized latex dispersions) are dosed to flocculate fine sticky particles and keep them suspended rather than adhering to fabrics. Due to variability in recycled contaminants, optimizing detackifiers is often mill‑specific.
Biocides (slimicides) complete the toolkit for microbial slime. Papermaking systems are warm, wet and nutrient‑rich; left unchecked, microbes foul wires and cause odor and corrosion (www.degruyterbrill.com) (www.degruyterbrill.com). Traditional programs use glutaraldehyde, isothiazolinones, and DBNPA (fast‑acting biocide) to disinfect whitewater loops and chest tanks. More targeted combinations (e.g., isothiazolinones + glutaraldehyde) and enzyme‑based alternatives are being adopted to meet environmental rules. Although microbial treatments “may appear as a costly offer,” their absence can lead to “large economic drain” from slime‑induced losses (www.degruyterbrill.com) (www.degruyterbrill.com). Optimized biocide programs are often monitored with online microbial sensors to minimize both slime and chemical waste; some mills even trial enzymes or bacteria‑lysing agents as eco‑friendly adjuncts to reduce biocide load.
Each specialty chemistry must be rigorously dosed and monitored. Automated dosing and sampling systems (flow‑paced injection, hygiene sensors) ensure consistent protection, where an accurate chemical dosing pump helps maintain targets. Mills use assays (stickies deposition tests, deposit monitors) to gauge deposit potential and adjust chemistries. In practice, deposit control integrates dispersant/detackifier programs in the wet end (stock forming section) and dedicated clean‑in‑place cycles (alkaline or acidic boilouts) during shutdowns.
Raw materials and water chemistry control
Raw material selection matters. Many high‑yield pulps contain more resin acids, so blending with bleached kraft pulps can reduce pitch load. Eucalyptus and acacia pulps generally have lower resin content than some softwoods (link.springer.com). Minimizing bark and knots and using freshly debarked chips cuts extractives; in recycling, stricter segregation of hot‑melt labels and waxed cartons, plus cold‑water adhesive use in paper products, reduces stickies entering the mill.
Water and chemistry control are pivotal. Softening make‑up water and controlling hardness limit calcium bridging of pitch (www.researchgate.net), where a softener mitigates calcium and magnesium. Maintaining optimal pH through the system affects resin acid solubility; mills often run slightly alkaline (pH ~8–9) to discourage pitch deposition.
Closed‑loop water systems must be cleaned periodically, since dissolved and colloidal substances (DCS) accumulate over reuse cycles. Good filtration in whitewater loops reduces free pitch and fines; a clarifier can remove suspended solids within typical detention times (clarifier). Flotation skimming is widely used to remove dispersed contaminants; dissolved air flotation provides high solids capture with compact footprint (DAF). Continuous debris removal stabilizes loops and reduces foulants on fabrics (automatic screen).
Mechanical and operational practices remain foundational: regular high‑pressure showers and vacuum boxes on wires/felts remove incipient deposits; scheduled chemical cleans of press felts (caustic or peroxide) keep them open. Recovery boiler cleaning (antiscalant programs, sootblowing) prevents fireside fouling that can send surges of solids into loops; a targeted scale inhibitor program supports this. Troubleshoot deposit hot spots with online deposit monitors or manual deposit clamps, and target them with bolt‑on fixes (side‑stream cleaning, frequent felt washing).
Program governance and ROI tracking
A robust chemical program pairs routine monitoring with ROI discipline. Mills apply a return‑on‑investment mindset: instead of price‑per‑kg, they calculate value in production yield, quality, downtime avoided and energy savings (www.pulpandpapercanada.com) (www.pulpandpapercanada.com). Small gains in runnability or a few percent higher production from fewer breaks often justify premium deposit‑control additives.
Regularly reviewing deposit metrics (cleaning frequency, shower frequency, sheet breaks) and correlating them with chemical dosages enables data‑driven fine‑tuning. Many mills pilot new chemistries; Archroma reports that after testing, some mills consolidated three older products into one dispersant, cutting chemical usage and reducing total cost (www.cleanroomtechnology.com).
Standards, compliance and regional context
Environmental regulations frame every decision. Indonesia’s pulp & paper mills (6th‑largest paper producer globally; www.universaleco.id) operate under strict standards (ISO 14001, green‑industry certifications, wastewater limits). Milieu rules push mills toward minimal‑waste processes: many have committed to 4R policies and closed‑loop water use (okipulppaper.co.id).
In practice, deposit‑control chemicals must be as safe and biodegradable as possible. Archroma highlights that its dispersant “complies with food contact regulations such as BfR and FDA” (www.cleanroomtechnology.com). Biocides must be handled as B3 (hazardous) waste under local law.
Measured outcomes and industry trends
Well‑run programs show measurable gains: reduced shutdown time (hours of cleaning per week cut by double digits), fewer sheet breaks, improved paper quality (lower speck count). One study (PW Consulting) notes that good deposit control (along with scale inhibition) can cut boiler fouling and energy use by 12–15% (pmarketresearch.com). Archroma’s tests found “significant cost savings” from simplifying deposit treatment (www.cleanroomtechnology.com). Industry surveys suggest an ROI approach to additives often identifies multi‑hundred‑percent ROI when speed or quality is the bottleneck (versus selecting only by chemical cost; www.pulpandpapercanada.com).
Key trends reinforce the need for deposit control. Wastepaper usage is rising: ~38% of fiber is now recovered paper, with projections for continued growth. Soft‑water markets (e.g., Asia, where hardness is low) increasingly demand advanced polymers over traditional talc or bentonite. Environmental scrutiny of biocides is tightening worldwide (e.g., EU Biocidal Products Regulation), pushing mills to optimize dosing and explore enzyme or biological slimicides as alternatives (www.degruyterbrill.com). In Indonesia specifically, the industry’s “Green Industry Standard” encourages both efficiency and safety, driving integrated programs that tie deposit control to waste minimization.
Figure‑quality monitoring (e.g., deposit sensors, sticky counters) and digital process control are on the rise, enabling preemptive adjustments. In sum, effective deposit control combines: (a) selecting low‑extractives raw materials, (b) optimizing process conditions (pH, water loop cleaning, equipment maintenance), and (c) applying the right mix of dispersants, detackifiers and biocides. Deploying these measures in tandem — with attention to ROIs and regulations — supports cleaner operation, higher uptime and lower total cost in modern papermaking.
Sources: Authoritative industry reviews and reports (Hassler 1995 (link.springer.com); Pathak et al 2021 (www.degruyterbrill.com)), specialty‑chemical case studies (www.cleanroomtechnology.com) (www.cleanroomtechnology.com), market analyses, and Indonesian industry data (www.universaleco.id) (okipulppaper.co.id) were consulted to compile these insights. Each recommendation above is grounded in documented mill experience and technical literature, ensuring practical relevance for engineering and procurement decisions.
