Cleaning is one of the most delicate and irreversible interventions in the restoration process: what is removed cannot be put back. Therefore, before considering any aqueous or solvent-based system, dry mechanical cleaning is almost always the first step, and in many cases the only one necessary to remove dust, soot, and loose surface deposits.
This guide covers the main dry cleaning methods used in conservation-restoration —from the gentlest to the most vigorous—, when each is appropriate, and what precautions you should not skip. It is intended for professionals: restorers of mural painting, paper, easel paintings, polychrome sculpture, and textiles.
What is dry cleaning and when should you choose it?
We talk about dry cleaning when we remove dirt without water or solvents, only by mechanical action: dragging, absorption, or sweeping of particles. It is the method of choice when:
- The dirt is superficial and non-greasy (dust, soot, environmental deposition, construction residues).
- The support or the paint layer is sensitive to water or solvents.
- The goal is maximum reversibility and the least possible addition of foreign material to the artwork.
It does not resolve embedded or greasy dirt —other systems are used for that—, but it avoids mobilizing moisture or solvents on layers that cannot tolerate them.
Principles to consider before touching the artwork
Regardless of the method, the same criteria apply in conservation-restoration:
- Minimum intervention and reversibility: always start with the least invasive method and increase intensity only if necessary.
- Prior testing in a discreet and representative area before applying generally.
- Never dry clean a powdery or disintegrated layer without consolidating it first: sweeping would remove the pigment. Consolidation comes first; cleaning, afterwards.
- Always remove residues (eraser crumbs or sponge debris) by vacuuming: if they remain on the artwork, they attract dirt and moisture.
- Neutral pH and sulfur-free materials, to avoid introducing compounds that may migrate or react with the original.
Dry cleaning methods, from least to most invasive
1. Soft brush + HEPA filtered vacuuming
The starting point and the least aggressive. A soft-bristle brush mobilizes dust, and a HEPA-filtered vacuum cleaner collects it without redepositing it. Protect the nozzle with a mesh to avoid dislodging loose fragments.
Caution: on unfixed powdery layers, even this sweeping can drag away paint material. If the surface "sheds," consolidate it first.
2. Dry cleaning sponges (vulcanized rubber)
So-called smoke sponges (vulcanized rubber) clean by gentle mechanical dragging, without water or solvent. They are very effective on soot, smoke, and dry, non-greasy dirt, and are a classic in mural painting and large surfaces.
How to use them:
- Gentle strokes in one direction, renewing the sponge surface as it gets dirty.
- Remove residues by vacuuming when finished.
- Do not use them on friable polychromy or fragile layers: they can dislodge material.
At Innovart, we use the Lascaux Wallmaster dry cleaning sponge, formulated for dry cleaning of mural paintings and surfaces.
Why we work with the Wallmaster: it doesn't crumble. It removes soot and dust by contact, without leaving crumbs or residue on the artwork, so you don't end up cleaning what the sponge itself has left behind. And when one side gets saturated, you cut off the outer layer and continue with a clean surface. It is Lascaux's smoke sponge, which is the brand we work with for this range.
3. Wishab / akapad type erasers
These are sponge-like erasers made of latex with factice (vulcanized vegetable oil), with a neutral pH in their soft versions, available in different hardnesses. They offer more control in localized cleaning than a large sponge.
What to keep in mind:
- They leave crumbs that must always be removed.
- Unlike the previous rubber sponge, these do leave crumbs, which must always be removed.
- They can become abrasive if you press too hard or if the layer is fragile: work with minimal pressure.
4. Erasers and rubies
For specific spots. As a general criterion, soft rubber erasers leave less residue than PVC ones, which can release plasticizers onto the surface. They also exist in powder or granular form, which are spread and moved gently over large surfaces (very commonly used on paper and graphic works).
For this spot cleaning, at Innovart we have a white PVC-free eraser, a Dust-Free residue-free eraser, a kneadable eraser, and a precision eraser pencil with a brush for specific spots. These are fine art erasers, not specifically for conservation, but they meet the important criterion here: little residue and no PVC. Pre-test and only on stable layers.
5. Sepiolite and attapulgite
These are absorbent clays. Their most common use is in poultices and pastes —where they are applied wet or semi-wet— and, dry, as absorbents for grease and dirt. They do not act by dragging, but by absorption.
Summary table
| Method | Purpose | Common supports | Key precaution |
|---|---|---|---|
| Soft brush + HEPA vacuuming | Dust and loose particles | All | Not on unfixed powdery layers |
| Vulcanized rubber sponge | Soot, smoke, dry dirt | Murals, large surfaces | Not on friable polychromy; remove residue |
| Wishab/akapad type eraser | Localized cleaning | Mural, paper, stable polychromy | Minimal pressure; remove crumbs |
| Erasers and rubies | Specific spots | Paper, graphic works | Soft rubber better than PVC |
| Sepiolite / attapulgite | Grease absorption | Stone, stone supports, mural | Is absorbent, not dragging |
Dry cleaning according to the support
- Mural painting and frescoes: natural territory for rubber sponges and cleaning erasers. In buon fresco (pigment on carbonated lime), the surface usually tolerates dragging better than in secco painting, which is more friable. Always watch out for areas with powderiness: consolidate before cleaning.
- Paper and graphic works: soft erasers, powdered erasers, and a soft brush; fine control and minimal pressure.
- Easel painting: dry cleaning removes dust and surface deposits; dirt embedded in the varnish requires other systems.
- Polychrome sculpture: brush and vacuuming as a rule; sponges and erasers only on stable polychromy.
- Textiles: micro-vacuuming with protective mesh as the reference method.
Common mistakes to avoid
- Increasing intensity without first trying the gentlest method.
- Dry cleaning a layer that actually needed prior consolidation.
- Leaving eraser or sponge residues on the artwork.
- Pressing harder to "clean more": in dry cleaning, more pressure = more risk of abrasion.
Do you have questions about which method to use in your intervention?
At Innovart, we select conservation-restoration materials with technical criteria and help you choose the right one for your case. Do you have questions? Write to us and we'll review it together: innovart.art · info@innovart.art