［装修：油漆］如何敛缝

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How To Caulk

Caulking has many uses and some limitations. Knowing how to caulk can improve the looks of a painted room, it can seal around the bathtub or shower and create a seal around doors and windows. Caulk provides a transition from one surface to another when the joint is not perfectly tight. Caulk will perform very well when filling cracks of up to 1/4 or 3/8 of an inch, beyond this width another product should be used to fill the void.

Types of caulk will include paintable or non-paintable. Most caulk used around the home is paintable acrylic caulk. After drying, this caulk will accept paint and the paint will adhere very well to the caulk. Non-paintable caulk, usually 100% silicone, cannot be painted. It should not be used next to walls, mouldings or any surface that may be painted. Paint will not adhere to 100% silicone caulk. The tube of any caulk will be labeled paintable or non-paintable.

The caulks of today from the major manufacturers are very durable and long-lasting. When properly applied they should last 20 to 40 years. Their main benefits are they will stay pliable, they do not harden, become brittle and crack. Caulk fills a void or crack and will flex as temperature changes cause expansion and contraction of the surfaces. Caulk does not prevent movement. If the surrounding surfaces are shifting, expanding or contracting then the crack will probably open. This is not a failure of the caulk but due to movement of the surfaces it is applied to.

The adhesion of caulk around a bathtub can be lost due to mold or mildew growing under the caulk. This is also seen in caulked joints around sinks and showers. The mold was probably present before the caulking was applied and continued to grow, causing the caulk to fail.

Here are some tips for a successful and good looking caulked joint.

   * Use caulk for cracks and voids that are less than 3/8 of an inch wide.
   * Do not caulk over dusty surfaces, wipe away the dust or apply a coat of primer to the surface.
   * Do not caulk bare wood surfaces. Caulk adheres best to primed or painted wood. The wood should at least be primed before applying the caulk.
   * Cut the tip of the caulking tube to small opening. A large hole in the spout allows too much caulk to flow out. Its messy.
   * If the crack is too small to accept caulk (seen often on window and door frames) use a putty knife to widen it enough to receive the caulk.
   * Use a slow, firm pull on the caulking gun's trigger. Keep the gun moving and ease up on the trigger near the end of the crack. Use the trigger release to stop the flow of caulk.
   * Use a wet rag to wipe off the end of the spout and to keep the your hands moist.
   * To smooth the bead of caulk use a moist finger wiping off the excess onto a wet rag.
   * Around wood mouldings use only enough caulk to fill the crack. When smoothing the caulk with a moist finger use enough pressure to shape sort of a corner in the joint. Try to avoid a rounded joint. A corner will be easier to paint and look much better.
   * Tubs, sinks and showers should be clean and dry before caulking. Mold, mildew and soap residue will cause the caulk to fail.
   * Caulk does not require priming before painting. Paintable caulk will accept finish coats of paint.
   * If caulking next to an area that will not be painted and a neat joint is desired, use low-tack tape to mask off the surface. Apply the tape as straight as posssible along side of the crack (both sides if neither surface is to be painted). Apply just enough caulk to fill the crack and come up to the edge of the tape. Then smooth the caulk with a moist finger removing the excess from over the crack and tape. Allow the caulk to partially dry and pull away the tape. If the crack was not sufficiently filled repeat the process spacing the tape slightly further away from the crack.
   * Caulking will shrink as it dries. Do not try to overfill a crack. A second application of caulk is sometimes needed. A second application is easier and will look much better than trying to overfill a crack.

Caulking takes practice and patience. It is messy and almost uncontrollable but it is the best product for neat, tight joints. Try these tips, they will help.

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Tip: always caulking in a sunny day instead of  a raining day!