The process of preparing the mixture requires cleanliness and precision, since even microscopic particles of dust or water can ruin the entire layer. Errors at the mixing stage often appear only after drying, when defects can only be corrected by completely repainting the element. In this instruction we will look at how to technically correctly prepare two-component varnish to work, what tools to use and how to diagnose problems by the appearance of the mixture.
System components and their purpose
Modern automotive paints and varnishes consist of several key ingredients, each of which performs a strictly defined function. The basis is yourself varnish (base component), containing acrylic resins and additives that provide gloss and elasticity. Without activation by a chemical reagent, this composition remains liquid and indefinitely sticky.
The second required element is hardener (catalyst). It is he who triggers the polymerization reaction, turning the liquid mixture into a durable, chemically resistant coating. The proportion of hardener is critical: too little will lead to a soft, under-dried film, and too much will lead to brittleness and rapid cracking.
Third component - solvent, which regulates the viscosity of the mixture for correct spraying through the spray gun. Depending on the ambient temperature and the size of the part to be painted, choose a “fast”, “medium” or “slow” solvent. Using the wrong type may cause the varnish to boil or, conversely, take too long to dry, resulting in dust build-up.
⚠️ Attention: It is strictly forbidden to mix varnishes and hardeners from different manufacturers. The chemical composition of the resins may differ, which will lead to separation of the mixture or lack of adhesion.
Necessary tools and preparation
To mix the components well, it is not enough to simply pour them into one container. You will need graduated measuring containers, special funnels with filters (usually 125-190 microns) and stirring sticks. The use of dirty containers from other chemicals is unacceptable, since solvent residues can change the properties of the mixture.
The optimal solution is transparent plastic measuring cups with a scale of proportions. This allows you to visually control the volume of each component. If the scale has worn off or is not clearly marked, it is better to purchase a new glass rather than risk ruining the material.
Before starting work, make sure that all components are at room temperature (approx. 20°C). Cold varnish and hardener have increased viscosity, which makes accurate dosing and initial mixing difficult. Also prepare personal protective equipment: respirator and gloves, as hardener vapors are toxic.
Mixing proportions and correspondence table
The most common scheme for HS varnishes is a 2:1 ratio, where two parts of the base account for one part of the hardener. However, there are other options, such as 4:1 or 3:1, which depend on the specific brand of product. The solvent is added as a percentage of the total mass of the mixture, usually 5-10%.
It is important to understand the difference between volume and weight, although in auto repair they often operate with volumetric indicators when using measuring cups. Dosing accuracy affects mixture lifetime (pot life) and final coating hardness.
| System type | Proportion (Base: Hardener) | Adding solvent | Mixture life time |
|---|---|---|---|
| HS (High Solid) | 2 : 1 | 0-10% | 2-3 hours |
| MS (Medium Solid) | 2 : 1 | 10-20% | 1-2 hours |
| Quick drying | 4 : 1 | 0-5% | 30-40 min |
| Heat resistant | 2 : 1 | 5-10% | 3-4 hours |
When mixing, always pour in the base first, then the hardener and finally the thinner. This makes it easier to control the process and avoid overflowing the container.
Step-by-step instructions: how to thin varnish
The process of preparing a working mixture requires a sequence of actions. Violation of the order can lead to uneven distribution of the catalyst in the volume.
- 🧪 Thoroughly shake the jar with the main varnish to lift the components that have settled to the bottom and even out the consistency.
- 📏 Measure the required amount of base into a clean measuring cup, observing the lower limit of the selected proportion.
- ⚗️ Add a strictly measured volume of hardener, watching the meniscus of liquid at eye level for accuracy.
- 💧 Pour in the required amount of solvent if the instructions or temperature conditions in the workshop require it.
- 🥄 Mix the composition intensively with a clean stick for at least 2-3 minutes, passing along the bottom and walls of the glass.
☑️ Checklist before mixing
After mixing, be sure to filter the mixture through a funnel with a mesh directly into the spray gun tank. This will trap any clots or debris that might get into the glass.
The nuances of working with small volumes
If you need a small amount of varnish for touch-up, use syringes to accurately dispense the hardener. An error of 1-2 grams at small volumes can significantly change the properties of the mixture.
Effect of temperature on viscosity and drying
The room temperature directly affects the viscosity of the diluted varnish. When cold, the mixture becomes thicker, which can lead to orange peel formation. In hot weather, the varnish becomes too liquid, which can lead to the formation smudges and reduced drying time.
To correct the behavior of the material, different types of solvents are used. The “fast” solvent evaporates more intensely and cools the surface, which is useful in hot weather, but dangerous at low temperatures. A “slow” thinner gives the varnish more time to spread, which improves pouring, but increases the risk of dust accumulation.
⚠️ Attention: Do not try to dilute thickened varnish with large amounts of solvent. This will reduce the dry residue and worsen the protective properties of the coating. Use only the recommended type of thinner.
The optimal temperature for application is considered to be in the range of 20-22°C. If the chamber is colder, the drying time will increase and the risk of moisture condensation will increase. In such cases it is advisable to use activated hardeners or heating the material.
Checking viscosity with a viscometer: For professional work, use a DIN4 viscometer. The varnish flow time should be 14-18 seconds at 20°C. This is more accurate than determining by eye.
Common errors and ways to resolve them
One of the most common mistakes is not mixing the ingredients properly. If hardener is distributed unevenly, matte spots or sticky areas may appear on the surface that will never dry.
Another problem is using old or improperly stored hardener. The hygroscopicity of some catalysts causes them to absorb moisture from the air and lose their properties. Always close jars tightly immediately after use.
- 📉 The appearance of craters: the reason is silicone contamination or oil getting into the mixture.
- 🌫️White coating (blooming): occurs due to high humidity or the use of a solvent that is too fast.
- 💧 Smudges: a consequence of diluting too thin or applying an excessively thick layer.
If you notice that the mixture has begun to thicken in the glass ahead of time (the pot life has expired), do not under any circumstances try to dilute it again. The chemical reaction has already begun, and adding a solvent will only spoil the structure of the polymer. This mixture must be disposed of.
The main secret of success: Prepare the polish in small portions, which you are guaranteed to use in 40-50 minutes. This will ensure stable viscosity and perfect pouring throughout the entire process.
Questions and answers
Is it possible to dilute the finished varnish if it has begun to thicken?
No, if the varnish begins to thicken, it means the polymerization reaction has begun. Adding a solvent will not stop the process and will not restore the properties, but will only damage the coating. The mixture should be thrown away.
What solvent is best to use for varnish in hot weather?
In hot weather (above 25°C) it is recommended to use a “slow” solvent to avoid boiling and drying too quickly, leading to shagreen. However, for HS varnishes, standard solvents are often used, adjusting the pressure on the gun.
How long does diluted varnish take to dry?
Touch-drying time is 30-60 minutes at 20°C. Complete polymerization and development of chemical resistance occur within 7-14 days, although drying in a chamber at 60°C speeds up this process to several hours.
Is it possible to mix varnish from different manufacturers?
Strongly not recommended. The chemical formulas of resins and hardeners between brands may be incompatible, resulting in peeling, clouding or lack of hardness of the coating.