Plastering is one of the last stages of finishing an internal or external wall. Applying plaster (or putty) is an extremely technical procedure that is usually best left to professionals, but each owner can do it himself as long as he follows some basic guidelines. Start by taking a good portion of dense, freshly prepared plaster, spread it over a clean wall using a trowel and then use a trowel to smooth the entire surface. After eliminating bumps and imperfections, the wall will be ready to be painted or covered with wallpaper.
Steps
Part 1 of 3: Prepare the Workspace and Materials
Step 1. Start with clean tools
One of the most important (and often overlooked) requirements for getting a professional plaster job is to avoid contamination. Before you start mixing the plaster, make sure buckets, trowels, trowels, and anything else you are going to touch the wall with are thoroughly clean. Wouldn't you use them to eat? Then I'm not good enough.
If even the slightest trace of plaster residue from a previous job comes into contact with the wall, it could interfere with the ability of the plaster to adhere to it or prevent you from laying it properly. If you want the chalk to harden slowly, use cold water, let it absorb and mix the mixture as little as possible. If you want it to harden faster, use hot water and mix a lot
Step 2. Put some protective sheets to keep the work area clean
Inexpensive cloth sheets (or plastic ones) will create a barrier against dust, splashes, and muddy footprints left by stepping on the plaster. It is possible that plastering will get very dirty, so this simple precaution can save you from having to clean thoroughly afterwards. If the plaster stains dark walls, you will have to wash them with wet rags afterwards as it is very difficult to remove.
- Gypsum can also damage or scratch wood or laminate floors, so be sure to cover them well.
- For bomb-proof protection, use painter's tape to attach the tarp directly to the floor beneath the wall.
- Once finished, roll up the protective sheets, take them outside and rinse them with a jet of water.
- The fall of the plaster from the tools is mainly due to too much water contained in the mixture. As you get better at preparing it you will see that you will fall less, you will get less dirty on your hands and you will have less to clean.
Step 3. Clean the wall to remove dust and debris
Scrub the wall from top to bottom with a dry, stiff-bristled brush. Focus in particular on the areas with the greatest accumulation of dirt or old layers of plaster. Once finished, wipe the wall with a damp cloth to pick up the material you brushed off.
- Apply a primer to the stained areas to make the plaster adhere well.
- Repair any cracks before plastering the wall.
- To check if the wall is ready for a new layer of plaster, run a finger across the surface. If it becomes covered with dust as it flows, it means that it is still dirty. Finally, it is useful to spray a little water on the wall to make the new plaster adhere to it better.
- Whether you need to cover an old wall or plaster a new one, you must always start by cleaning the surface to be worked, otherwise the residues of dust, soap, oil, tar or mold would prevent the plaster from adhering to it. In addition, a wall that is too dry would absorb the water contained in the plaster causing it to harden before having time to fix to it.
Step 4. Apply some vinyl glue to the wall with a brush; it will serve to make the plaster adhere better
Put 1 part of vinyl glue and 4 parts of water in a disposable bowl and mix everything well. Spread the glue on the wall using a roller or a brush, trying to cover it entirely. For best results, apply chalk when the glue layer is tacky but not quite dry.
- The vinyl glue is used to adhere the new plaster layer to the wall.
- Applying a preparatory layer to the substrate will also prevent the humidity of the plaster from penetrating it, which could cause it to crumble.
Step 5. Prepare the plaster in a 19 or 26 liter bucket
Fill it halfway with cold, clean water. Open a package of plaster mix and pour it into the bucket until a mound forms on the surface of the water. Then with the handle of a plunger (or other mixing tool) it begins to incorporate the dry plaster particles.
- Always add the plaster mix to the water, not the other way around. Adding water to the chalk will require you to apply more force to mix the one at the bottom of the bucket, and mixing it too much will cause it to harden too quickly for you to use. Stir the dough as you add the chalk.
- Using an electric drill with a mixing blade can save you a lot of time if you have to mix multiple buckets or large amounts of plaster. But be aware that mixing the mixture with a drill attachment will cause the plaster to harden faster, so use it for larger jobs that require you to use larger quantities in a short time. If you're only doing minor touch-ups, use a smaller bucket and mix the chalk by hand, so it hardens more slowly and gives you time to work.
Step 6. Stir the plaster repeatedly to make it thicken
Keep stirring until the dough is perfectly homogeneous and free of lumps. From time to time, scratch the inside of the bucket to remove any dried lumps. Once finished, the plaster should have more or less the same consistency as a spreadable cream.
A great way to determine if the chalk is thick enough is to stick a wooden stick into the bucket to mix the paint. If it stands alone, your cast is perfect
Part 2 of 3: Apply the first layer of chalk
Step 1. Put some fresh chalk on the sparrow hawk
Take a small amount of chalk out of the bucket using the tip of the trowel. If you've transferred the plaster to another surface, such as a tarp or workbench, you can simply slide it onto the sparrow hawk from there. Pile up some so you don't have to interrupt your workflow to add more.
The plaster should not stick to the sparrow hawk if it has been properly mixed, but you can wet the surface of this support a little to make it easier to detach
Step 2. Use the trowel to prepare a small amount of plaster
Slide the trowel under the pile of plaster and collect enough of it to apply a floor-to-ceiling layer. If you want to be precise and efficient, make sure that the chalk is right in the center of the trowel.
Start by taking a small amount of chalk and then add more as needed. It is much easier to layer gradually than to level out too bulky dough
Step 3. Spread the chalk on the wall, starting at the bottom corner
Bend over and press the plaster onto the wall in a gradual arcing upward motion, lifting as you reach the upper areas. Once the upward motion is complete, slide the trowel over 5 to 8 cm of plaster, then reverse the motion and work downward. Keep using this technique to level the chalk out little by little.
- If the plaster is soft and is dripping a little from the wall, let it harden for 5 minutes, then go over it again with the trowel and you will see that it will not run anymore.
- Don't keep the trowel parallel to the wall, but tilt it slightly so you don't risk removing the plaster with each pass.
- With the first coat try to make a layer about 1 cm thick.
Step 4. Plaster the wall by dividing it into sections
Continue to work along the wall, spreading the plaster from the bottom up and stopping each time you need to add more on the sparrow hawk. Repeat this procedure until you have covered the entire surface evenly.
- You may need a stepladder to reach the highest points on the wall.
- Don't worry too much about getting perfect thickness at this stage of the job. Later on you will go to further level the plaster finishing everything.
Step 5. Smooth out the first layer of plaster
Once you have applied the first layer of plaster, clean the trowel and pass it on the wall in all directions. Apply even pressure, focusing on where the chalk is thickest or where raised lines have formed. Imagine that you are coating a cake with icing: with each pass the surface must be more refined and leveled.
- If necessary, use a sprayer to re-moisten the first few sections of plaster, so it will be easier to spread it out with a trowel.
- A good, moistened brush can come in handy for touching up corners and tricky spots.
Step 6. Scratch the plaster to make the surface rougher before adding a second layer (optional)
It can be helpful to scratch the wet chalk to create a better base for the second coat. Scratch the entire surface vertically using a plaster scraper or notched trowel. Now that you've made the base a little rougher, you no longer have to worry about the second layer of plaster cracking or peeling.
- If you don't have these tools, you can also use a common fork (but it may take longer).
- By scratching the wall you will create shallow grooves that will increase the overall surface and make the second layer adhere better.
Part 3 of 3: Spread and Refine the Second Layer
Step 1. Apply a second and final coat of chalk
Even the "shaving layer" can be 1 cm thick, but you can also get away with it by making it 2 mm. Roll it out exactly like the previous one, making sure that there are no gaps or lines that are too obvious.
You can smooth this layer with the trowel or replace it with a trowel for the finishing touches
Step 2. Use a trowel to achieve an even finish
Gently slide it over the damp plaster surface working in all directions to remove any bumps, lines, holes or imperfections. Once finished, the wall should have a smooth and uniform appearance.
- Proceed calmly; Smoothing plaster is a painstaking and tiring job, but it is important to get it done correctly.
- Be careful not to smooth the plaster too much. It may begin to take on a shiny appearance which would reduce the grip of the paint or wallpaper.
Step 3. Let the plaster harden
Depending on the different conditions, gypsum can take 2 to 5 days to harden completely. Avoid touching it as it dries, as any imperfections that appear during this time will be visible on the finished wall.
- Factors such as the composition of the gypsum, the temperature of the work area and the amount of moisture in the air can affect drying times.
- The wall must be completely dry before you can cover it with paint, wallpaper or any other decoration.
Advice
- Beginners should use sand-based putty (plasticizer) for the first layer. It is much easier to work with and hardens slower.
- Use putty for the external walls and plaster for the internal ones, because if there is a lot of humidity it will crumble. If you apply plaster in a damp room, such as a kitchen or bathroom, be sure to use a moisture resistant paint, otherwise it will eventually crumble over time. To carry out repairs (quick or any other type) in bathrooms and kitchens, but also to repair eaves, grout and cover, you can use white concrete because it does not crumble with water. The drawback of white cement is that it cannot be sanded after it has hardened; each hand you give must therefore be smooth. However, applying a more diluted final layer than the previous ones makes it easier to obtain a smooth surface.
- Gypsum does not shrink much and is easy to sand. Interior putty is even easier to sand, but you have to wait 24 hours for it to dry. Also, it shrinks a lot and you will be forced to apply it again to get rid of cracks. Plaster and plaster for interiors are products that cannot be used outdoors because they deteriorate with humidity.
- Practice on a small area of the wall to perfect the technique.
- Before applying plaster to weathered wood and brick walls, cover them with a wire mesh so that it will adhere better and last longer.
- Plastering is a job that requires a lot of time, a lot of dexterity and experience. If you don't feel confident in your abilities to do the job properly, you'd better hire a professional.
- Don't forget to meticulously clean your tools when you finish the job.
Warnings
- In many ways, working with plaster is a race against time. You will have to do some precise work to avoid making mistakes, but you will not have to be so slow that you allow the plaster to dry before you are done.
- Do your best to get the job done right on the first try. Repairing poorly done plaster can be very expensive.
