If you work in conservation-restoration, Paraloid B-72 is probably the consolidant you've held in your hand most often.
In this guide, we review what it is exactly, how it's prepared, how to apply it step-by-step, the most common mistakes, and in which situations it's best to choose it over other options.
What is Paraloid B-72?
Paraloid B-72 is an acrylic copolymer of ethyl methacrylate and methyl acrylate, with a predominance of ethyl methacrylate. It comes in translucent granules or beads that dissolve in organic solvents to create consolidating or adhesive solutions. This composition gives it chemical stability, transparency, and long-term reversibility.
Properties that make it essential
- Long-term chemical stability: it does not yellow or become brittle over time. Accelerated aging studies confirm its stable behavior for decades.
- Total reversibility: it dissolves easily in acetone, ethanol, or mixtures of both, even after a long time.
- Water-free: unlike water-based consolidants, B-72 in solvent does not add moisture to the substrate, which is critical when working on easel paintings or hygroscopic supports.
Common concentrations
| Concentration | Application |
|---|---|
| 2-3% | Fixative / preconsolidation of powdery layers |
| 5% | Standard consolidation of pictorial layers |
| 10% | Consolidation of porous materials |
| 15-30% | Adhesive for joining fragments (ceramics, archaeology) |
Recommended solvents
- Acetone: dissolves B-72 quickly. It is the most common solvent, but its rapid evaporation can promote blooming in humid environments; in such cases, mixtures with ethanol or slower-evaporating solvents are used to control drying.
- Ethanol: slower, longer working time.
- Acetone/ethanol mixture (1:1): balance between speed and working time. Widely used in laboratories.
How to prepare and apply Paraloid B-72 step-by-step
Preparation is simple, but the order matters to avoid lumps and obtain a homogeneous solution.
- Calculate the weight/volume (w/v) concentration. A 5% solution is 5 g of granules per 100 ml of solvent. Weigh the granules before starting.
- Add the granules to the solvent, not the other way around. Pour the solvent into the container and drop the beads in. If you do the opposite, the granules tend to clump at the bottom.
- Allow to dissolve without stirring initially. B-72 swells and dissolves on its own in a few hours (sometimes it's best to leave it overnight). Gentle stirring at the end helps to homogenize; stirring from the start generates foam and microbubbles that remain in the film.
- Protect yourself and ventilate. Acetone and ethanol are volatile and flammable: work with adequate ventilation or localized extraction, nitrile gloves, and for prolonged applications or in enclosed spaces, respiratory protection with an organic vapor filter. Keep away from heat sources.
- Apply as appropriate. By impregnation with a brush or by dripping for consolidation; with a syringe for punctual adhesion of fragments. Apply thin layers and allow the solvent to evaporate between coats instead of applying a single thick layer.
- Control the finish. At high concentrations or with excess product, a surface sheen may remain. If this occurs, it can be smoothed out with a pass of the solvent.
Common mistakes when using Paraloid B-72
- Too high a concentration for pre-consolidation. In powdery layers, a very concentrated solution stays on the surface and forms a film without penetrating. For fixing, reduce to 2-3%.
- Applying to a damp substrate. B-72 in solvent does not mix with water: if the support is damp, consolidation will fail. Other options are better suited here (see next section).
- A single thick layer. Solvent trapped under a thick film takes a long time to evaporate and can cause blooming. Several thin layers are better.
- Confusing the granules with a ready-to-use product. B-72 is sold in beads precisely so that each restorer can prepare the concentration and solvent needed for their intervention.
When to choose Paraloid B-72 over other options
B-72 is the first choice when the substrate cannot tolerate water and maximum reversibility is needed. When the substrate is damp or cannot tolerate organic solvents, water-based alternatives such as Lascaux 498-HV or Primal AC-33 may be more suitable.
Frequently asked questions about Paraloid B-72
How long does a prepared Paraloid B-72 solution last?
Stored in a tightly sealed container at room temperature, the solution remains usable for a long time. If the solvent partially evaporates and the solution thickens, simply readjust by adding more solvent.
Is it reversible once dry?
Yes. One of its main advantages is that it redissolves with acetone or ethanol even after a long time, allowing for removal or re-intervention of the consolidation. This is why it is a reference material under the criterion of reversibility in conservation-restoration.
Can it be used as an adhesive as well as a consolidant?
Yes. At high concentrations (around 15-30%), it works as an adhesive, commonly used for joining ceramic and archaeological fragments. For consolidation, much lower concentrations are used.
Which solvent should I choose, acetone or ethanol?
It depends on the working time you need. Acetone evaporates very quickly (useful when you want it to dry soon); ethanol gives more handling time. The 1:1 mixture is a widely used balance.
At Innovart, you can find Paraloid B-72 and other reference consolidants in our collection of adhesives and consolidants for restoration. If you have questions about which concentration or solvent suits your intervention, write to us at info@innovart.art and we will guide you.