Now you have your tools and materials ready. This section provides the exact techniques for a permanent repair. Follow these five steps carefully to transform that persistent crack into a seamless, invisible part of your wall.

Step 1: Prepare the Crack for Repair

Proper preparation creates a solid foundation for your patch. You must give the joint compound a stable area to bond with the drywall. A simple hairline crack does not provide enough surface area for a strong repair.

1. Create a V-Groove: Take your utility knife and carefully cut a V-shaped groove along the entire length of the crack. The groove should be about 1/8 to 1/4 inch wide at the surface. This step removes any loose drywall and creates a channel for the compound to fill.
2. Remove Debris: Use a shop vacuum or a damp cloth to clean all dust and loose material from the groove and the surrounding area. A clean surface is essential for proper adhesion of both the tape and the mud.

Why this works: The V-groove allows the hot mud to penetrate deeper into the wall. This creates a much stronger mechanical bond, preventing the old crack from reappearing through your new repair.

Step 2: Apply the Self-Adhesive Tape

The self-adhesive nature of fiberglass tape makes this step quick and straightforward. Unlike paper tape, you do not need to apply a preliminary layer of mud.

Start at one end of the crack. Center your Fiberglass Drywall Joint Tape directly over the V-groove you created. Press the tape down firmly as you unroll it, ensuring it makes solid contact with the drywall surface along the entire length of the repair. When you reach the end, cut the tape cleanly with your utility knife.Run your 6-inch drywall knife flat over the tape with firm pressure. This action fully activates the adhesive and removes any air pockets, guaranteeing the tape lies perfectly flat against the wall.

Step 3: Lock it in with the First Coat of Hot Mud

This first coat is the most critical. Its purpose is not to hide the tape but to lock it into place and create a super-strong base. You will use your setting-type compound, or "hot mud," for this step.

• Mix Your Mud: Prepare a small batch of hot mud in your mud pan. You want a consistency similar to thick peanut butter. Remember, you have limited working time before it hardens.
• Apply the Mud: Load your 6-inch drywall knife with mud. Apply it over the tape using firm, even pressure. Your goal is to force the compound through the open mesh of the tape and completely fill the V-groove underneath.
• Smooth the Surface: Once the tape is filled, make another pass with your knife held at a slight angle. This will remove excess mud and leave a thin, smooth layer over the tape. Do not worry about building up the surface yet. You should still be able to see the mesh pattern of the tape through the thin layer of mud.

Let this coat harden completely according to the manufacturer's instructions. Do not try to sand hot mud at this stage.

Step 4: Build and Feather the Finishing Coats

After your first coat of hot mud has hardened, you can begin building the surface. The goal of these next coats is to create a wide, thin layer of compound that makes the repair invisible. You will use your wider 10-inch or 12-inch drywall knife for this process. For these finishing coats, you can switch to an all-purpose joint compound, which is easier to sand.

Apply a thin second coat of compound over the repair. Extend this coat a few inches beyond the edges of the first coat. Hold your knife at a low angle and pull it smoothly across the surface. Immediately make a second pass to remove any excess compound. This technique is called "feathering." It creates a tapered edge that blends into the wall.

Mastering the Feathering Technique：Feathering is the key to an invisible patch. Apply pressure to the outer edge of your drywall knife while leaving the inner edge (closest to the repair's center) almost floating. This action presses the mud thinly at the edges, making it disappear into the surrounding wall surface.

Allow the second coat to dry completely. For the third and final coat, apply another very thin layer. This coat should be even wider than the second one. A wide, well-feathered repair is much harder to detect after painting.

• Your second coat should extend the repair area to about 12-16 inches wide.
• Your final coat should bring the total width to approximately 20-24 inches for a truly seamless blend.

Let this final coat dry for at least 24 hours before moving on to the next step.

Step 5: Sand, Prime, and Paint for a Flawless Finish

You are now on the final stage of your repair. Careful work here will ensure the crack vanishes completely, leaving a perfect surface for paint. This is where your professional-grade repair using Fiberglass Drywall Joint Tape truly becomes invisible.

First, you will sand the dried compound. Use a medium-grit (120-150) sanding sponge. Apply light, even pressure and sand in a circular motion. Your goal is to smooth out any ridges or imperfections. Run your hand over the area. It should feel perfectly smooth and level with the surrounding wall. If you feel any bumps or edges, continue sanding lightly until they disappear.

If your wall has a texture, you must replicate it to make the patch blend in.

1. Apply a small amount of spray-on texture or thinned joint compound to the repaired area.
2. Practice on a scrap piece of cardboard first to match the texture pattern and thickness.
3. Once the new texture is dry, you can lightly sand it down with a hand sander to match the height of the existing wall texture.
4. Feather the edges of the new texture into the old texture to create a seamless transition.

Next, you must prime the repair. This step is not optional. New joint compound is very porous and will absorb paint differently than the rest of your wall, a problem called "flashing." Priming seals the patch and creates a uniform surface. A high-quality polyvinyl acetate (PVA) drywall primer is designed specifically for this purpose. It creates a synthetic film that seals the porous mud and ensures your paint adheres properly. For the best results, look for a 100% acrylic primer-sealer, which eliminates any chance of the repair showing through your final paint coat.

Finally, you can paint. Apply one or two coats of your matching wall paint over the primed area. Feather the paint at the edges to blend it into the rest of the wall. Once dry, step back and admire your work. You have not just patched a crack; you have created a permanent, invisible repair.