Introduction
Jim Brower wrote a fine set of general rules for cleaning some specific common substrates. Following is a combination of his comments with this author's comments: Solvent cleaning should always be done with a dispenser bottle (never a pan of solvent) and two rags method (one rag to put it on and another to take it off). Priming should always follow the advice of the sealant supplier.

Stone
Many stone surfaces are contaminated with dust and fines from cutting. They may be contaminated by cutting oils or old sealants. Loose dust is best removed by wiping with a solvent cloth. Attached fines and other bonded impurities will need wire brushing, water blasting, sandblasting, or grinding. Blowing the joint clean with oil-free air and a solvent wipe will probably be used as well. Lastly, the jint should be wiped with a dark cloth to see if it is clean. Some stone will need priming before using with certain sealants.

Glass and Porcelain
Clean glass and porcelain with methylethyl ketone, alcohol, or an alcohol/water mixture. Some sealants exhibit excellent unprimed adhesion; others will need primers. Old glass with sealant, paint, or other bonded surfaces need the foreign material cut off as close to the glass as possible. A razor is the usual tool. Then they can be solvent-cleaned with methylethyl ketone or xylene (xylol) until the contaminant appears to be removed. Then the surface should be re-cleaned as if it were new glass, with another solvent wipe.

Painted or Lacquered Surfaces
Painted or lacquered surfaces will be of different composition depending on the specific coating and how long it has weathered. Most sealant manufacturers will have recommendations as to whether a primer is generally needed or not, but the variability of the surface almost guarantees that a field test should be run.

In all cases a solvent wipe will usually be indicated. The choice of solvent will depend on the coating, since some solvents soften and weaken some coatings. Consult the paint suppliers, if the sealant supplier cannot recommend a proper solvent for cleaning. In fact, a paint supplier may be a good first choice for cleaning advice.

Peeling or Flaking Paint
The sealant must be adhered to a sound surface. Loose paint, chalk, etc., must be removed as a first step.

Rigid Plastics
Rigid plastics are an ever-increasing part of the construction (and glazing) industry. While most of these will need a solvent wipe and many will need a primer as well, these materials are prone to permanent damage from some solvents. The damage may be quite severe, with crazing and stress cracking from a single solvent contact. It is always advisable to contact the plastic supplier as well as the sealant supplier before proceeding with these substrates.

Flexible Plastics and Rubber
Adhesion to flexible plastics and rubbers is often difficult to obtain. These substrates generally release plasticizers, which must be removed before sealant and/or primer are applied. VM & P naptha is a good first choice of solvent. Methylethyl ketone (MEK) ia also a good solvent, but care in its use is warranted because some plastics are damaged by strong solvents. A good first step is to call a plastics or rubber supplier followed by a call to the sealant supplier. The first call should yield a list of acceptable cleaning solvents and the second a list of sealants that have been known to adhere to these types of plastics and rubbers.

Most (not all) well-weathered plastics and rubbers can be adhered to if they are clean.

Mill Finish Aluminium
Mill-finish aluminium often carriers an invisible oil film and many times a loose oxide layer. Clean with a good degreasing solvent such as xylene or trichlorethylene. In some cases abrasion with steel wool or emery paper is needed, followed y a solvent wipe. Many sealants need primers for adhesion to mill-finish aluminium.

Anodized Aluminium
Anodized aluminium is generally a better surface for adhesion than mill-finish aluminium in that after a normal sealant wipe, many sealants will adhere unprimed. Methylethyl ketone (MEK) and xylene are common cleaning solvents for anodised aluminium. There is some variability in the anodising process, and in critical applications a field test for adhesion is advised. Sometimes primers are required.

Copper
Copper often as a heavy oxide film (patina), wich can be removed chemically but most often for simple sealing is removed by sanding or abrading with steel wool. Solvent cleaning is generally required, even if the surface is abraded. Some sealants, such as acid-curing silicones, are not to be used with copper; others, such as some neutral silicones, give unprimed adhesion. Consult the supplier to determine if the chosen sealant is compatible and if a primer is needed.

Steel
Most steel will be painted, and the paint should be well adhered to the steel. Thus proceed as recommended for a painted surface.

If the steel is not painted, it should be cleaned of dust, oil and rust. Rust is often removed by sandblasting or sanding. Dust and oil are removed by naptha, Methylethyl ketone (MEK), or xylene. Even if the steel is new and bright, a solvent wipe is needed.

Some sealants will need a primer, and the recommendation of the supplier must be followed. Some sealants are not recommended for use on raw steel.

It is possible for rust to start to bloom and adhesion be destroyed if the steel is kept in high humidity or submerged conditions. Thus, checking adhesion with time on raw steel is a good practice.

Stainless Steel
Stainless steel is sometimes a difficult material for adhesion. It will always need a solvent wipe and will often need a primer, although some of the new neutral silicones and some of the acrylics may give unprimed adhesion. Be sure to contact the supplier for primer recommendations.

Galvanized Steel
It is sometimes difficult for a sealant to adhere to galvanized steel, even if the steel is cleaned and primed. Some sealants, such as some of the new silicones, give unprimed adhesion after a wipe with a degreasing solvent such as xylene or toluene. Some sealants, such as an acid-curing silicone, are not to be used or should be used with a great deal of caution and a primer and then only after checking with the sealant supplier.

Unpainted Wood
Unpainted wood is a difficult and variable substrate. Many water-resistant woods, such as teak, redwood and cedar, contain a lot of neutral oils that make adhesion difficult, though possible. For these woods, a primer is generally needed; some sealants will not be recommended, even with a primer. Consult the supplier.

All wood surfaces must be dry, sound and dust-free to obtain adhesion, but solvent wiping is not generally needed. Care should be exercised and the adhesion to wood checked on regular occasions, since most woods can absorb water readily and good initial adhesion can be lost with time.

Concrete
Concrete must be sound and able to hold a bond. If it is fresh concrete, it must be allowed to dry. If it is powdery or poor grade concrete, the surface must be strengthened. The concrete must be cleaned of dust and fines using the same instructions as for stone. Most sealants will need a primer. The very-low-modulus silicones generally will not need to be primed. The concrete must be free of oils, coatings and penetrants, or adhesion must be tested with these contaminants in place. A solvent wipe is generally a needed final step.

Few sealants are recommended for concrete below grade, and these generally with special primer and for specific primer and for specific nonstraining conditions. Be sure to contact the sealant supplier for instructions for below grade use.