When and why to apply aqueous aracite solution to wood

Even if the theme meeting in Sibiu with carpenters was socializing, many technical topics were also discussed, and some of them were related to wood finishing and derived panels. Someone brought up the use of aracite solution in the sanding process. It was the starting point of a debate about the purpose of using aracite solution, pros and cons and professional materials with which similar results are achieved. Seems like a topic of interest to woodworkers and wood enthusiasts, so I reprint it below.

Why and how to use aracite solution

The main purpose of using the aracet is blocking the absorption of the berry deep into the wood, which makes much more uniform colouring. It was a method widely used in factories in the past, especially in those making doors with profiled frames or profiled furniture. In the profiled areas, on the stiles as they used to say in the past, there are a lot of fibre ends, the colour absorption in the wood is very high and the area is much darker than the rest of the furniture. The aracite solution is absorbed into the wood, the adhesive molecules (PVA - polyvinyl acetate) get into the wood where they harden. This forms a barrier in the wood that prevents absorption deep into the wood, with the colour remaining only in the surface area of the wood.

The solution is also used as a sealant for milled MDF or tannin wood. However, it is not the best solution because aracite is not very waterproof. When applying water-based products there is no guarantee that the tannin will not come out of the wood or that a large amount of paint will not be absorbed into the milled area.

There are many who believe that the glue solution is used to improve sanding because after application, the wood grain rises. This is actually a side effect. Being a water-based solution, the absorption into the wood is high and the grain lifts. This makes sanding easier and improves the uniformity of staining and subsequent adhesion of film-forming materials (primer/lacquer/paint). But the same effect is obtained if wet grinding, i.e. before sanding the surface is wiped with a cloth dampened with water without abrasive.

The aracite solution is obtained by mixing one part aracite with 3 or 4 parts water (concentration 20-25%). Use ordinary aracite, not the hardening kind (mono or bi-component). Apply the solution with a brush, sponge, cloth or spray. After application, the wood is allowed to dry for 2-5 hours, depending on workshop conditions. It is a water-based solution so room temperature and air circulation are important. After drying, the wood is sanded and the stain or paint is applied.

Pros and cons

The arguments in favour of using aracite solution are low price, ease of application, lack of solvents (volatile organic compounds VOCs), a formaldehyde and other hazardous substances. It's a handy solution, especially for those doing DIY projects, but also for carpenters who are new to wood finishing.

However, since it is a product made for a completely different use - gluing wood - its behaviour over time can be unpredictable, especially when it comes to sealing (insulating) tannin in wood, knots and MDF. Great care must be taken when dosing because too much aracite in water can lead to the formation of a film that reduces the adhesion to wood/MDF of subsequent layers.

Liviu C., a specialist in abrasives, draws attention (in his comments) to a phenomenon that can occur when mechanically sanding panels to which an abrasive solution has been applied: "Arracite can lead to blackening of wood when sanding. This phenomenon generally occurs, as an example, when calibrating spliced panels where there is an excess of uncured adhesive at the time of splicing. This surplus of glue/wax generates a burning phenomenon in the calibrating machine, both on the wood surface and on the calibrating abrasive belt. When sanding by hand it may not occur, but when sanding mechanically due to the speed of the abrasive this phenomenon occurs."

Alternative

Sthe hellac and insulators are safer alternatives for sealing wood and regulating absorption. Shellac is a very good alternative for sealing the knots or wood so that the tannin does not escape on the surface. It is frequently used by model-making, inlaying, marquetry enthusiasts because it does its job very well, and after drying (removing the alcohol from the varnish solution) the wood can be finished with oil or any kind of varnish.

In the case of production of wood or MDF furniture for commercial use, my recommendation is to use professional insulators. Any company that sells professional wood varnishes and paints has such products in its portfolio. Using them as directed eliminates the risk of subsequent defects.

There are also alternatives to using aracite solution to achieve uniform colouring. A handy option is to apply a thin first coat of thinned primer and then apply the stain. Use the primer to be applied to obtain the film and the dilution is at least 1:1. No film should form when applying it. After drying, sand and apply the primer. Another option is to use coloured varnishes. The disadvantage in this case is the less natural, plastic-like appearance. The professional option is to use even-grain varnishes which are made in such a way that they do not go deep into the wood. This prevents stains from appearing or showing through. wood growth defects.

I hope you find the above information useful. As usual, additions are welcome. And if you have any questions or queries, please leave them in the space below. I'm sure I'll reply.