The situation when you open a can of paint, and instead of liquid you find a thick mass or even jelly, is familiar to many craftsmen. Acrylic enamel - the material is capricious, and if storage conditions or expiration dates are violated, it is prone to polymerization. However, you should not throw away the expensive composition, since in most cases it can be revived and returned to working condition.
The main task when diluting is not just to make a slurry, but to restore the chemical balance binder and solvent without damaging the polymer structure. Incorrectly selected chemistry can cause the coating to become cloudy after drying, become covered with shagreen, or even peel off from the metal. Therefore, before pouring in the first liquid you come across, you need to understand the nature of the thickening.
In this article we will take a detailed look at which chemical compounds are suitable for various types of acrylic enamels, how to determine the degree of suitability of paint for restoration and what proportions are optimal. You will learn why water is not suitable everywhere, and when it is better to use specialized solvents.
Reasons for thickening of acrylic enamel
Understanding the cause of a problem is half the solution. Acrylic paints are a complex emulsion where polymer microparticles are suspended in an aqueous or solvent environment. The first sign of the onset of irreversible processes is often a change in viscosity. If the enamel begins to thicken immediately after opening, the seal of the package may have been broken and some of the solvent has evaporated.
A more complex case is a chemical reaction triggered by time or temperature. When stored in frost or, conversely, in direct sunlight, acrylic polymer may begin to coagulate. In this case, the particles stick together to form flakes. If, when stirred, these flakes do not dissolve but remain in lumps, then, alas, the material is lost.
⚠️ Attention: If hard lumps have formed in the jar that cannot be broken up with a stirrer, or a sharp sour smell of sour milk has appeared, such enamel cannot be used. It will no longer lie flat and will not protect the body.
It is also worth considering the type of enamel. One-part formulations (1K) dry by solvent evaporation and can be thinned many times before they turn to stone. Two-component enamels (2K) with a hardener do not last long - usually 2-4 hours after mixing. An attempt to dilute a “two-component” that has already begun to set will lead to defective coating.
To diagnose the condition of the paint, take a clean wooden stick and try to stir the contents. If the mass is homogeneous but thick, the chances of salvation are high. If you feel the resistance of lumps or see separation into a clear liquid and a dense sediment, the degradation process has gone too far.
Main types of solvents for acrylic
The choice of thinner directly depends on the enamel base. In the automotive and construction industries, two types of acrylic materials are most common: water-dispersible and solvent-soluble. It is absolutely impossible to confuse them, since the chemical reaction can be unpredictable.
For water-based acrylic enamels, which are often used for decoration or priming, the main thinner is pure water. However, in auto repair, more durable compounds based on organic compounds are more often used. Here they come into play specialized solvents, such as 646, 647, 650 or R-12.
- 💧 Distilled water: Suitable only for water-soluble acrylic primers and some interior enamels, not recommended for automotive topcoats.
- 🧪 Solvent 646: an aggressive mixture of esters, alcohols and ketones, perfectly dilutes many types of enamels, but can change the gloss.
- 🛡️ Solvent 650: a softer composition, specially designed for diluting acrylic varnishes and enamels, preserves the shine of the coating.
- 🏭 Branded thinners: products from the paint manufacturer (Mobihel, Duxone, Vika), which guarantee the preservation of all the properties of the material.
The use of universal solvents such as acetone or white spirit is only permissible in extreme cases and for rough work. Acetine evaporates too quickly, which can lead to shagreen (orange peel), and white spirit takes too long to dry and can leave a greasy residue.
The best solution is always to purchase the original thinner of the same brand as the enamel. The chemical composition of branded products is ideally balanced to interact with a specific type acrylic resin. This is especially important for metallics and pearlescents, where the wrong solvent can ruin the orientation of the flakes.
How to dilute enamel by brand (Compatibility table)
The car enamels market is crowded with various brands, and each manufacturer may have its own recommendations. Below is a table of compatibility of popular brands of acrylic enamels with various types of solvents. This will help you navigate if you don’t have the original product at hand.
| Enamel brand | Recommended solvent | Alternative | Features |
|---|---|---|---|
| Mobihel | Mobihel Standard 0860 | Solvent 650 | Requires precise proportions for gloss |
| Duxone | Duxone DX-500 | Solvent 647 | Tolerates dilution well, but is afraid of moisture |
| Vika | Vicat solvent 650 | Solvent 646 (caution) | Budget enamel, sensitive to the quality of the thinner |
| Brulex | Brulex 285-00 | Solvent 650 | Quick drying, requires quick action |
| Reoflex | Reoflex 0860 | Solvent 647 | Universal acrylic enamel, stable in operation |
When using alternative solvents, always perform a compatibility test. Mix a small amount of enamel with the selected thinner in a transparent container and leave for 15-20 minutes. If the mixture does not curdle, bubble or change color, it can be used.
Therefore Always apply the first layer very thinly (“foggy layer”)to check the reaction of the materials.
Dilution ratios and viscosity
The key parameter for successful painting is viscosity. Paint that is too thick will look like shagreen, and paint that is too thin will run or leave a small “dry residue.” To measure viscosity, a device called a viscometer (most often a Ford-4 funnel) is used. For acrylic enamels, the optimal flow time is 18-22 seconds at a temperature of 20°C.
If there is no viscometer, experienced craftsmen use the “by eye” or “stick” method. Properly diluted enamel should flow from the stirrer in a continuous stream, which at the end breaks off, forming a drop. If the paint drips frequently and intermittently, it is thick. If it pours like water, it’s too much.
Standard dilution proportions are as follows:
- 🎨 For a spray gun (spray gun): 10-15% solvent from the volume of enamel. This ensures perfect atomization and flow.
- 🖌️ For brush or roller: 5-10% solvent. A thicker consistency is needed here to avoid drips.
- 🔫 For priming: Dilution up to 20% is allowed for better soil penetration.
The solvent should be introduced gradually. Add 5-7% of the volume, mix thoroughly, and only then evaluate the result. You can add a thinner to paint already mixed with a hardener only within the “viability” of the mixture (usually no more than 1 hour).
☑️ Checking paint readiness
Technology for restoring thickened paint
The process of resuscitating paint requires care and consistency. You should not pour solvent directly into a common jar if you are not sure of the result. It is better to pour the required amount into a separate clean container.
First, thoroughly mix the thickened enamel. If there is dense sediment at the bottom, it needs to be “lifted” and stirred until smooth. Then add the first portion of solvent (about 5% of the volume). Stirring must be vigorous so that the solvent molecules penetrate the polymer structure.
⚠️ Attention: Do not use metal objects for stirring if you are working with small volumes, so as not to introduce rust. It is better to use wooden or plastic stirrers.
After initial mixing, let the paint sit for 10-15 minutes. Acrylic needs time for the solvent to start working. If the viscosity does not decrease, add another portion of thinner. Repeat the procedure until the desired consistency is achieved.
What to do if the paint has curled?
If, when adding a solvent, you see that the paint has flaked or curled up like cottage cheese, the process is irreversible. This mixture can only be used as an anticorrosive agent for hidden cavities, having first been filtered through a nylon stocking, but it will not hold onto the body.
Be sure to filter the restored enamel before pouring it into the spray gun tank. Use special funnels with a mesh or a regular nylon stocking. This will remove any undissolved particles that could clog the spray nozzle.
Dilution errors and their consequences
The inexperience of the master often leads to common mistakes that are costly. The most common of these is the use of incompatible solvents. For example, adding nitro-enamel solvent to acrylic can cause instant clouding of the varnish or enamel.
Another mistake is over-dilution. Trying to save paint or make it more fluid, craftsmen pour solvent “by eye”. As a result, the coating becomes matte, loses color depth and becomes fragile. Acrylic film is formed only with the correct ratio of dry residue.
Temperature is also often ignored. In summer, you need to use “slow” solvents so that the paint has time to spread before drying. In winter, on the contrary, “quick” compositions are required, otherwise the enamel may not have time to form a film and become overgrown with dust or dullness.
- 🌫️ Cloudiness (Whitening): occurs due to moisture or the use of too fast a solvent in the heat.
- 🍊 Shagreen (Orange Peel): a consequence of too thick paint or incorrect pressure in the spray gun.
- 💧 Drips: the result of over-thinning or applying too thick a layer.
- 🎨 Different tone: may appear if the solvent aggressively affects the pigment, changing its shade.
To avoid these problems, always read the technical documentation (TDS) on the enamel can. There, the manufacturer indicates the recommended types of solvents and proportions for various temperature conditions.
If you are thinning paint in a cold room in winter, warm both the enamel and the thinner to room temperature (20°C) before mixing. This will improve their mutual dissolution.
FAQ: Frequently asked questions
Is it possible to dilute acrylic enamel with gasoline or kerosene?
Strongly not recommended. Gasoline and kerosene contain oily fractions that do not evaporate completely. This will cause the coating to remain sticky, collect dust, and may never dry completely. Use only solvents intended for this purpose.
How long can already diluted paint be stored?
If it is one-component acrylic (without hardener) and the jar is hermetically sealed - several months. If a hardener is added to the paint, its “life” is limited to 2-4 hours (maximum 24 hours in a tightly closed container, but the properties will be worse). Water-dispersed paints, after dilution with water, are best applied on the same day.
How to wash acrylic enamel from hands or tools?
Fresh acrylic enamel (especially water-based) can be washed off with warm water and soap. If the paint has already begun to dry out or is organic-based, you will need solvent 646, 647 or a special paint remover. For hands, it is better to use special cleansing pastes (“Auto Scrub”) so as not to dry out the skin with acetone.
Why did the paint lose its shine after thinning?
This may be due to the use of a too aggressive or fast solvent, which disrupted the polymerization process. High humidity in the room may also be the cause. To restore shine, sometimes polishing after drying completely (after 24 hours) or applying acrylic varnish on top helps.
Is it possible to mix acrylic enamel from different manufacturers?
It is undesirable to mix bases (colored enamels) from different manufacturers due to possible chemical incompatibility of the binders. However, one brand's thinner (eg Mobihel) is often suitable for another brand's enamel (eg Vika) if the chemical base is the same (both are 650 type). But it’s better not to take risks and stick to one product line.
The main secret of success is not to skimp on solvent. A cheap thinner can ruin expensive paint and the entire job, requiring the part to be repainted.