The kind of joint compound you apply depends on a variety of factors. You will first need to decide whether to use powder, a dry from that takes mixing with water, or redi-mix all purpose mudd.
Estimate the square foot to be that the mudd is the cover. Normal approximate ranges are 400 to 600 sq foot per 4.5 gallon bucket. If there is a high proportion of seams/joints to be covered, or an out of a concentration of butt joints, lean towards having an excess on hand. If the ceiling is to be stomped or receive another texture, don’t forget to take this into account and this should not be done with powder mixes due to their set time and formulated consistency. Of course any garage areas could take a roller texturing.
The chemical powders, or timed dry mixes, are mixed with clean warm water. These are suited for patches, where speed is of the essence, or in conjunction with certain mesh tapes. You can mix a work time for as few as 15 minutes and longer work durations. Add a little water into the pan prior to pouring in the powder compound to help eliminate bottom-stick.
Mix the mudd to a consistent batter (the topping blend will have greater workability). Too tight a mix won’t level off properly, will dry too soon, and will not form a base devoid of air in which to bed the tape. Turning too thin a mix will encourage improper drying. While the dry mix, considered by itself, simply can’t be expected to acheive the creamy consistency of other compounds,. Often it will carry a grainy consistency and, dry to a comparative rough texture. Also be prepared to exert a greater sanding effort as the chemicals within the mix tend to dry the compound to greater hardness. This effect can be accentuated by the more time that is allowed to pass beyond being ready for sanding.
Be aware that dry time guidelines for hot mudd do have exceptions, such as mudding to a depth, or in lower ambient temperatures. This will affect the successive mudd coats that are applied as well.
All purpose is just that. You can bed the tape with it, top coat with it, or skim corner bead given its bonding capabilities. Although as a top coat, all-purpose typically will not provide a base for achieving the same smoothness as does topping compound per se. As with all compounds, if thinning is needed, always add clean warm water. And again, too thick or watery a blend will have consequences. A good idea is to err on the side of less water. Keep in mind that many compounds should not be reconstituted.
A true topping compound when applied correctly will go on like thick cream. It the most effortless to work with, and requires the least amount of abrasion from sanding, to shape and contour. Topping compound is not designed for bedding tape.
Beware of increased humidities, these will affect dry times and work cycles/ the wait periods till the next coat. Note: caution should be excercised when adding bonding agents to the mix and should only be reserved for those with experience.
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