These instructions apply for any unsealed blueboard that has some tooth to it. To check for the presence of a sealer,  mist the surface lightly. If the water beads up and does not soak in immediately, follow the instructions for sealed surfaces.  If the surface does not have sharp tooth to it, also go to the instructions for sealed and slick surfaces. Blueboard joints do not need to be taped and mudded.

Maintain temperatures between 45 and 90 degrees Fahrenheit for 3 days before, during, and for 3 days after application.

Prepare wall:

Scrape back any flaking or crumbling blueboard until you have a solid, well bonded surface.   Knock off any ridges or protrusions over 1/16 inch with a scraper. Depressions over 1/8 inch  should be daubed even with surface.

Check to be sure that corners have a slight radius or greater and correct if necessary.

If present, clean off any dust, dirt, grease, oil, and other foreign matter and deposits that could impair the bond with the plaster.

Protect adjacent surfaces with painter’s tape, drop cloths and/or plastic.

Taping and Mudding (Optional)

Blueboard joints do not need to be taped and mudded. However, if the joints are already mudded with joint compound, you will need to prime the joint compound (skip to the priming instructions below). Should you choose to tape and mud, you have two options:

Standard taping procedure, followed by priming:

Reinforce joints with joint tape (jute, paper or fiberglass scrim) and a standard joint compound to a Level 2. (Drywall screws do not need to be covered and the joint compound does not need to be sanded. Ridges and protrusions up to 1/16 inch and depressions of  up to 1/8 inch are acceptable.) Once joint compound is dry, prime it using the instructions that follow.

Use American Clay Earth Plaster to tape joints, no priming needed:

Tape joints using jute, paper or fiberglass scrim and American Clay Earth Plaster (see mixing instructions below) to a Level 2. (Drywall screws do not need to be covered and the mud does not need to be sanded. Ridges and protrusions up to 1/16 inch and depressions of  up to 1/8 inch are acceptable.)  Allow mudded seams to dry completely. Mist wall seams prior to plastering the entire wall with the first coat of American Clay.

Priming Joint Compound on Blueboard

Confirm that the joint compound is dry.

Any patches of joint compound, if present, should be covered with one of the following primers:

1. American Clay Earth Plaster Primer

2. PVA (polyvinyl acetate) concrete or plaster bonder, such as El Rey Gypsum Bond, USG Plaster Bonder or Omega PVA Bonder. Sharp mason’s sand (#30 or smaller) should be added to PVA primers around cornerbeads, trim and other vulnerable areas. Joint compound requires two coats of  PVA primers. Please note: most PVA primers must be plastered within 2 hours -14 days after they are applied, depending on the primer used.

3. A good quality wall primer mixed with 2 cups sharp mason’s sand (#30 or smaller) per gallon.

All of these primers may be brushed, rolled or sprayed on. Any sanded primer (including the American Clay primer) that is sprayed on must be backrolled.

Mix Plaster:

Each 50 lb. container of American Clay is mixed with approximately two gallons of water. You may need a bit more or a bit less of the water to bring the plaster to the correct consistency (similar to pudding).

Start by measuring 1 & 3/4 gallons of water into a five gallon bucket or a wheelbarrow.  Slowly pour in one 50 lb. container of American clay. Let this sit for five minutes.

If you have a separate pigment, add 1 cup or more of the remaining water to the pigment container and stir well to create a smooth, thick paste. Empty the paste onto the soaking plaster, rinse the container with a bit of the water, and add it to the soaking plaster also.

Mix with a drill and plaster paddle or a hoe. Continue to add water and mix thoroughly until the color is even and the plaster is the consistency of pudding. (You may need slightly less or slightly more water than the two gallons).

For best results, allow the plaster to stand for 30 minutes before using. Workability improves with age, and additional water may be added to return thickened or dried plaster to a pudding consistency.

General Application:

The recommended application is two thin coats to create a combined thickness of 1/16 to 1/8 of an inch.

Mist with water any American Clay Earth Plaster that was used to tape the seams. (Do not mist any other part of the walls.) Apply the first thin coat of American Clay Earth Plaster with a trowel. Leave sufficient texture for the second coat to key in to the first coat. Let dry a minimum of 12 hours.

Lightly mist the first coat of earth plaster with water and apply the second coat. Let dry a minimum of 12 hours.

Finishing an earthen plaster is probably the most important step. After drying, the second coat may be finished by rubbing it with a barely-damp sponge or by lightly misting the surface and working it with a stainless steel trowel, rubber float or horsehair brush. This compacts and strengthens the surface, reduces trowel marks and preventing dusting. Additional finishing techniques special effects are demonstrated on the American Clay video.

Clean Up:

Tools can be cleaned up with water. Unused wet plaster can be laid out to dry. It may be rehydrated at a later date, mixed thoroughly, and used for touchups.

Sealing:

It is not necessary to seal this plaster except in areas that are regularly exposed to  splashing water (around sinks, bathtubs and shower stalls) or splattering oils (behind stoves).

Recommended sealers include paste waxes such as Trewax or Bioshield Floor and Furniture Hardwax, liquid potassium (water glass) products such as AFM Safecoat Penetrating Waterstop, and acrylic masonry sealers such as Okon W-1.