## 1 Introduction
### Aim and Organization of This Work  
Let us first consider the chemical-physical characteristics of the main component of these formulations, BAI, and how these influence the application properties. The identification codes of this solvent are as follows: CAS 100-51-6, CE 202-859-9, Index-No. 603-057-00-5, REACH No. 01-2119492630-38-XXXX.  
From the point of view of safety and toxicity impact, the alcohol has good characteristics that make it attractive in practical use: the Regulation (EC) No 1272/2008 reports a low-risk classification. Precisely, signal word: warning; hazard statements: H302 + H332 Harmful if swallowed or if inhaled; and H319: Causes serious eye irritation [16]. A specific study reports that the alcohol has low acute toxicity, with an LD50 of 1.2 g/kg in rats. It oxidizes rapidly in healthy individuals to benzoic acid, conjugated with glycine in the liver and excreted as hippuric acid [17].  
The high flash point value (101 \({}^{\circ}\)C--DIN 51758) classifies it among the solvents with a low risk of flammability. Also, for the environmental impact, the risk of bioaccumulation is low: this substance/mixture does not contain components considered to be persistent, bioaccumulative, and toxic (PBT) or very persistent and very bioaccumulative (vPvB) at levels of 0.1% or higher. It is described as readily biodegradable: from the partition coefficient (n-octanol/water, log Pow 1.05 at 20 \({}^{\circ}\)C), bioaccumulation is not expected.  
These interesting features, however, are balanced by others that may be of concern from an application point of view. Unfortunately, this solvent was not considered by [PERSON] in the important work of determining the evaporation-retention curves of solvents applied to the surface of a traditional oil painting on canvas [18]. However, based on the high boiling point (205 \({}^{\circ}\)C) and low vapor pressure (0.07 hPa at 20 \({}^{\circ}\)C) it is reasonable to expect strong retention in a composite system such as an easel painting. And this long retention, combined with the high solvent power, can cause interference with paint media of various nature, causing swelling and extraction of mobile components, low molecular weight molecules, even with high polarity (mono- and dicarboxylic acids, metal soaps). Another relevant issue is the consideration of BAI miscibility with water: perhaps there is excess optimism and a bit of superficiality in the common affirmation of its insolubility in water. The real data are 4.29 g in 100 mL of water at 20 \({}^{\circ}\)C [19]. This represents a non-negligible value, which implies that small quantities of the alcohol in water are not emulsified in it but form a hydro-alcoholic solution; larger quantities will be partially in emulsified form but always with a certain percentage dissolved. Operationally, simple visual observation already confirms this fact: only quantities of BAI greater than approximately 5% in an aqueous gel modify its transparency and make it milky-white exactly like an emulsion. The study of the action of hydroalcoholic solutions has never been explored in depth; however, logic tells us that their action can be profoundly different from that of an emulsion. In the specific case, BAI itself has a broad field of action, but it is not ionizing and dissociating; dissolved in water, it also acquires these actions, and its solvent power increases but in an unpredictable manner, perhaps also affecting inorganic materials (for example, pigments in the paint layer and inerts in the ground layer).  
The purpose of this work was twofold. Firstly, to analytically verify whether the physical form of an o/w emulsion really made the solvent action of BAI more controllable. Secondly, to establish whether the mutual immiscibility of BAI and the D5 siloxane, already demonstrated in our previous study [20], permitted the latter to be used as a further protective barrier of the paint layer, allowing for a more superficial action of the alcohol. Figure 1 shows the complete experimental phases.