Only plasterboards with prefabricated or manually processed edges are suitable for jointing with the product. Plasterboards with prefabricated edges must be jointed with a gap of 3–5 mm. When cut, edges of plasterboards should be profiled at 45°, treated with K-15 primer and fitted while maintaining a gap of 1-2 mm. Before joining, make sure that edges are prepared as required. Plasterboards should be clean, dry and securely attached. The product can be applied to all typical building substrates for filling and patching, including gypsum plaster, cement, lime, gypsum blocks, concrete, aerated concrete, plasterboards and durable coatings of emulsion, phthalic and oil paints, provided the substrate is stable, clean and dry. The surface should be stable, clean, free of grease, soot, flaking and unstable paint coatings (cleaning with water under pressure or detergents). Wetting of the substrate is not recommended as it reduces the adhesion of the product. No priming is necessary. If the substrate stability is uncertain, it is recommended to use the ŚMIG K-15 Universal Primer.

The product should be mixed with water (0.3 l of water per 1 kg of product) and mixed with a slow mixer and agitator suitable for gypsum finish. During preparation, use clean, preferably potable water. Put product into water, never the other way round. Mix until you reach uniform mass of desired density. After 2-3 minutes, the mixture is ready for use. Too thin or too dense mortar may be corrected during the initial 10 minutes by adding the dry product or water and mixing. To prepare mortar, use stainless containers free from any remains of solidified gypsum. Apply manually using clean stainless steel tools. Working temperature ranges between +10 and +40°C. 

Fill the space between the edges with D-3 using a spatula at an angle to allow the product to be accurately pressed into the gap. Allow to dry. When the product is used on plasterboards with manually cut edges and joints exposed to high stress, it is advisable to apply reinforcement tape. Tape should also be used to reinforce joints between plasterboards and other surfaces. Wait at least 24 h after jointing, before applying another D-3 layer. After drying, provide sanding with polycarbonate mesh or 80-150 grit sand paper and remove dust. It is recommended to finish the surface using ŚMIG D-1 or A-2 finish. Remove dust before painting. D-3 does not require priming. However, to improve the quality of paint coating, it is recommended to improve surface absorption of plasterboards and joints by applying K-15 multipurpose primer.

ŚMIG D-3 is also suitable for strengthening mineral plaster. For this purpose, apply a 2-3 mm layer of the product with reinforcement tape. Tape should be applied with a minimum overlap of 5 cm. The reinforcement layer is suitable for smoothing sanding as standard plaster. 

Repair the surface by pressing the product into the cavity. After drying, apply the second layer. For perfect smoothness, sand the surface with polycarbonate mesh or 80-150 grit sandpaper. Before applying another layer of plaster, as well as before painting, remove dust or prime the surface with ŚMIG K-15.