Grey modelling cardboard

Physical properties

Laser processing

Grey cardboard is made from recycled cellulosic fibres (mechanical and chemical wood pulp) without plastic coatings. Combustion fumes are cellulosic, non-toxic. Smell of burnt paper. Standard extraction is sufficient.

CO₂: CO2 laser cutting is excellent due to the dense, compact structure that lacks knots or internal voids like wood. The thickness (usually 1–3mm) requires medium power (15–30W) at moderate speed. Excellent for architecture, set design, and structural packaging. Engraving produces a clear, very precise light/dark contrast.

Diode: The dark grey colour of the cardboard absorbs the diode laser well. Good results on thicknesses up to 1.5mm with a 10W+ laser.

Fiber: Not applicable.

CNC / milling processing

Not workable with CNC and rotating milling bits: the compressed structure would crush and tear under tool stress. It is cut exclusively with orthogonal cuts via laser or blade.

Plotter and thermoforming

Workable with a plotter using specific deep blades for thick materials. The typical thickness (1–3mm) requires high pressure and blades with a suitable profile. Multiple passes may be needed for thicknesses above 2mm.

Post-processing

Sanding: Can be sanded with medium-grit sandpaper to even out cut edges. The dense structure of grey cardboard accepts sanding better than common cardstock.

Gluing: Excellent bonding with PVA glue, contact adhesive, or strong double-sided tape. The porous structure of grey cardboard ensures fast and strong adhesion. Extensively used in bookbinding for the boards of hard covers.

Over time: Grey cardboard is made from non-neutralised recycled fibres: it tends to yellow and acidify over time. It may warp due to humidity variations. For long-term archiving, prefer acid-free cardboards.

Common defects

• Warping from moisture absorption in untreated recycled fibres
• Laser cut edges with more visible carbonaceous residues than coated board
• Acidification over time with yellowing of untreated surfaces

Safety

Highly flammable like all cellulosic materials. Keep air assist active during laser processing to prevent embers in the dense material.

Availability and formats

Commercial formats: A4/A3/50×70cm sheets in thicknesses 1–3mm, rolls for bookbinding

Related materials

Sources

• ISO 9706 — Paper permanence and durability requirements
• Manuali operativi FabLab per modellismo architetturale e scenografico