Suction Table Applications in Paper Conservation

1. What Is a Paper Suction Table?

A paper suction table is a specialised conservation device that draws air downward through a porous working surface.

The object is placed over:

• blotting material;
• a screen;
• another porous support,

and suction creates a pressure differential across the sheet.

Canadian conservation training literature describes the basic effect clearly: paper and blotter are held in close contact, while solvents, dissolved dirt or treatment solutions can be drawn through the object into the absorbent layer below.

The table therefore provides controlled through-plane flow.

This can help a conservator localise treatment that might otherwise spread laterally across the sheet.

2. Why Suction Is Useful

When liquid is applied to paper without suction, it can move by capillary action in multiple directions.

This may produce:

• tide lines;
• stain migration;
• spreading of soluble degradation products;
• uncontrolled solvent movement.

Suction changes the pressure gradient.

Instead of allowing the liquid to travel primarily sideways, the table encourages movement downward through the paper and into the blotter.

This does not eliminate risk.

It gives the conservator another way to control the treatment.

3. Main Paper-Conservation Applications

Suction tables may be used for:

• local washing;
• reducing stains;
• extracting soluble degradation products;
• applying selected solvents;
• controlling bleaching or reducing agents in specialised treatments;
• humidification;
• flattening;
• drying;
• lining or attachment procedures;
• local pulp infill or leafcasting adaptations.

The exact method depends on the object and the conservator’s treatment plan.

A suction table is a platform for controlled treatment—not a single treatment method.

4. Local Washing

Local washing can be useful when an object cannot be fully immersed or when treatment is needed only in a selected area.

A basic approach may involve:

1. supporting the sheet on an absorbent blotter;
2. masking surrounding areas if required;
3. applying water or another selected solution locally;
4. using suction to pull the liquid through;
5. replacing saturated blotter;
6. monitoring the stain or degradation product.

This can reduce the distance that dissolved material travels laterally.

Media testing remains essential

If inks, pigments or annotations are water-sensitive, local washing can still cause movement.

Suction does not make soluble media insoluble.

The treatment should be preceded by testing and controlled application.

5. Stain Reduction

Suction can be particularly valuable when the objective is to reduce a local tide line or stain.

The conservator may use:

• water;
• buffered solutions;
• solvents;
• gels or mist application;
• another reagent appropriate to the stain.

The table can help draw solubilised material away from the treated area.

However, stain treatment is chemically complex.

The cause of the stain should be understood before selecting a reagent.

The goal is not necessarily to make the paper visually white.

It is to improve stability or appearance without unacceptable damage to cellulose or media.

6. Solvent Treatment

Some adhesives, tapes, oils or stains require organic solvents.

A suction table can help control solvent penetration and reduce lateral spreading.

This is useful, but introduces significant safety requirements.

Organic solvent treatment may create:

• vapour exposure;
• flammable atmospheres;
• dissolved adhesive migration;
• tidelines;
• changes to inks or coatings.

A table intended for solvent work should be compatible with the chemicals used and integrated with appropriate ventilation.

Local suction through the object is not automatically equivalent to safe laboratory fume extraction.

7. Drying and Flattening

Suction can support controlled drying.

By holding the paper against a flat porous surface, it may help reduce:

• cockling;
• local lifting;
• distortion.

The technique can be useful after:

• washing;
• humidification;
• local aqueous treatment.

However, excessive restraint can also create stress.

The conservator should control:

• suction level;
• moisture gradient;
• drying rate;
• edge restraint.

Very fragile or dimensionally unstable objects may require an alternative drying method.

8. Lining and Attachment

Vacuum or suction tables have also been used in lining procedures.

Suction can:

• hold layers flat;
• help remove trapped air;
• draw adhesive through porous layers in some techniques;
• support even contact during drying.

The suitability depends on:

• object media;
• adhesive;
• lining tissue;
• porosity;
• required pressure.

No single lining method is appropriate for all works on paper.

9. Local Suction and Suction Discs

Not every treatment requires a full table.

A small suction disc or masked working area can concentrate pressure beneath a limited region.

Local suction is useful when:

• a stain is small;
• the surrounding media are sensitive;
• the sheet is very large;
• treatment should avoid unnecessary wetting.

AIC and CCI literature documents local suction approaches for stain reduction and specialised treatment.

The smaller the active area, the greater the control can be—but the risk of hard treatment boundaries or tide lines must also be considered.

10. Masking the Working Area

Masking controls where air can pass through the table.

If the entire porous surface remains open, much of the airflow may bypass the object.

Masks can:

• concentrate suction;
• define the active treatment region;
• reduce unnecessary airflow;
• improve consistency.

Materials used for masking should be chemically and physically suitable for the treatment.

Sharp mask edges may create abrupt wet/dry boundaries, so treatment technique still matters.

11. Suction Level and Uniformity

There is no universal suction setting for paper conservation.

Required pressure depends on:

• paper porosity;
• object size;
• blotter;
• screen resistance;
• treatment liquid;
• whether the task is drying, washing or solvent extraction.

The table should provide adjustable control.

More suction is not automatically better.

Excessive pressure can:

• deform weak paper;
• pull fragments;
• emboss a screen pattern;
• accelerate drying too aggressively;
• move media;
• create uneven local treatment.

Uniformity across the active area can be as important as maximum pressure.

12. Surface Design

A conservation suction table should provide:

• flat support;
• even airflow;
• chemically resistant construction;
• a screen or porous layer appropriate to paper;
• access for blotter replacement;
• adjustable suction;
• cleanability.

Some designs use stainless-steel screens or perforated surfaces.

The working support should not imprint texture into damp paper.

Interleaving and blotter selection are therefore part of the treatment system.

13. Risks and Limitations

Potential risks include:

Tide lines

If a treatment boundary dries unevenly, dissolved material can concentrate at the edge.

Over-cleaning

A stain may be part of the object’s history. Aggressive reduction can produce an unnaturally clean patch.

Media movement

Soluble inks, dyes or retouching may bleed.

Paper distortion

Differential wetting can cause expansion and cockling.

Chemical damage

Bleaches, reducing agents or solvents may harm cellulose or media if poorly selected.

Mechanical loss

Strong suction can disturb weak fragments.

The suction table improves control, but professional judgment remains essential.

14. Safety

Treatment planning should consider both the object and the operator.

Depending on the process:

• provide local exhaust for solvent vapours;
• use compatible electrical equipment;
• manage flammable liquids;
• wear suitable PPE;
• prevent reagent spills entering equipment;
• define safe waste handling;
• maintain filters and pumps.

The table should be installed according to the chemicals and laboratory conditions in which it will actually be used.

15. A Typical Treatment Workflow

Assess

Identify the paper, media, stain or treatment objective.

Test

Test solubility, colour change and response in a small area.

Prepare

Select blotter, mask, suction level and reagent.

Treat

Apply liquid gradually while maintaining controlled downward flow.

Observe

Watch for tidelines, media movement, colour change or distortion.

Stop

Remove excess liquid and replace contaminated blotter.

Dry

Use controlled suction or another appropriate drying method.

Document

Record the solution, treatment area and outcome.

16. Selecting a Suction Table

Consider:

• maximum sheet size;
• required active area;
• suction adjustability;
• airflow uniformity;
• solvent compatibility;
• filtration or exhaust interface;
• work height;
• lighting;
• masking options;
• cleaning and maintenance;
• integration with other paper-conservation tasks.

A conservation laboratory may benefit more from a versatile, controllable table than from maximum suction alone.