# Modified kraft lignin as sustainable consolidants for waterlogged archaeological wood

## TL;DR

This study explores modified kraft lignin as a sustainable alternative to petroleum-based materials for preserving waterlogged archaeological wood.

## Contribution

The novelty lies in evaluating acetylated and encapsulated kraft lignin as eco-friendly wood consolidants for archaeological preservation.

## Key findings

- Acetylated lignin reduced water uptake significantly and improved dimensional stability moderately.
- Encapsulated lignin limited shrinkage and preserved natural wood color better.
- Modified lignin shows potential to replace petroleum-based consolidants in archaeological wood treatment.

## Abstract

This study evaluates lightened kraft lignin: modified via acetylation and encapsulation, as a sustainable consolidant for waterlogged archaeological pine (Pinus sp.) from the Biskupin site (Poland). Lignin was acetylated with acetic anhydride/pyridine and, in a separate route, converted into colloidal capsules by tetrahydrofuran/water self‑assembly; both modifications were characterized and then applied to waterlogged archaeological wood by 2‑week immersion. Effectiveness was assessed by Fourier‑transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), colourimetry, linear dimensional change (LDC), anti‑shrink efficiency (ASE), and water‑uptake tests. Acetylated lignin penetrated more deeply and reduced water uptake (from > 240% to ~ 96%) with moderate improvements in dimensional stability; encapsulated lignin showed limited penetration but lowered shrinkage (tangential: from 6.78 to 4.21%; radial: from 3.36% to 2.37%) through a surface‑barrier effect and was better in preserving the natural colour. These results indicate that modified kraft lignin, particularly the encapsulated formulation, can complement or partially replace petroleum‑based consolidants and motivate further optimization of capsule size/distribution to enhance mechanical performance and treatment uniformity.