Marking materials remover

Disclosing waxes or pressure indicating pastes, are used in fitting a dental appHance to estabhsh the location and extent of high spots or pressure areas, as on impressions and complete dentures. They are very soft, salve-like compositions that are painted onto the tissue side of an impression or denture. When the wax-coated denture is seated in the mouth, the soft paste is forced out of the areas showing hard contact between the denture and the mucous membrane. These areas on the denture can be easily marked and material removed from the denture to reheve the premature or hard contact. 

The level of alcohol-extractables remaining on the fiber also decreased as washing temperature increased (Figure 2). However, the quantity of material removed at the lowest wash temperature was significant and did not increase markedly with increases in wash temperature. Apparently, little would be gained in using the higher temperatures to remove these types of extractables. 

Influence of Solvents. The stress-strain curves of untreated and ether-extracted corneum in water show marked differences (81). Untreated corneum, extended 5% and relaxed, shows hysteresis similar to that observed for other keratinaceous structures (Figure 35). The deformation mechanism is completely reversible, and hydrogen-bond breakdown and slow reformation may be the major factors determining the stress-strain relationships. With ether-extracted samples, complete recovery is observed from 5% extension but with little or no hysteresis. The more rapid swelling and lack of hysteresis of ether-extracted corneum in water may be related to the breakdown of hydrogen bonds normally shielded from the eflFects of water by the lipid-like materials removed by ether. 

Chlorine, sulfur and zinc are potentially harmful chemical elements. Paints and crayons used to mark susceptible alloys must contain low quantities (measured in parts per million, or ppm) of the harmful chemical elements. Less than 100 ppm is allowable. Even if approved marking materials are used, they should be removed from areas that are to be welded, brazed or soldered. An approved solvent such as a non-chlorinat-ed type should be used to remove marking materials. The same principles apply when adhesive-backed tapes are used to fix items to stainless and nickel alloy products (e.g., for radiography). All traces of adhesive must be removed from the surface with an approved solvent. There are no restrictions on using fiber tip markers because they do not leave solid residue. Solvent removal is not required with fiber tip markers. 

Marking coated plastics is a multi-step process in which the first marking pass removes the majority of the top coating. The remaining residue is removed with a second, lower power pass to minimize the effect to the underlying material. For precise edge definition, the outline... 

Impurities in a corrodent can be good or bad from a corrosion standpoint. An impurity in a stream may act as an inhibitor and actually retard corrosion. However, if this impurity is removed by some process change or improvement, a marked rise in corrosion rates can result. Other impurities, of course, can have very deleterious effec ts on materials. The chloride ion is a good example small amounts of chlorides in a process stream can break down the passive oxide film on stainless steels. The effects of impurities are varied and complex. One must be aware of what they are, how much is present, and where they come from before attempting to recommena a particular material of construction. 

All processes may be classified as batch, continuous, or semibatch depending on how materials are transferred into and out of the system. Also, the process operation may be characterized as unsteady state (i.e., transient) or steady state, depending on whether the process variables (e.g., pressure, temperature, compositions, flowrate, etc.) are changing with time or not, respectively. In a batch process, the entire feed material (i.e., charge) is added instantaneously to the system marking the beginning of the process, and all the contents of the system including the products are removed at a later time, at the end of the process. In a continuous process, the materials enter and leave the system as continuous streams, but not necessarily at the same rate. In a semibalch process, the feed may be added at once but the products removed continuously, or vice versa. It is evident that batch and semibatch processes are inherently unsteady state, whereas continuous processes may be operated in a steady or unsteady-state mode. Start-up and shut-down procedures of a steady continuous production process are examples of transient operation. 

The term erosion-corrosion is used to describe the increased rate of attack caused by a combination of erosion and corrosion. If a fluid stream contains suspended particles, or where there is high velocity or turbulence, erosion will tend to remove the products of corrosion and any protective film, and the rate of attack will be markedly increased. If erosion is likely to occur, more resistant materials must be specified, or the material surface protected in some way. For example, plastics inserts are used to prevent erosion-corrosion at the inlet to heat-exchanger tubes. 

The results of this situation can be readily foreseen. A requisition for a specific item is occasionally filled with an item which, at first glance, appears to be the one requested but, actually, was formulated for a different purpose and is either inadequate or dangerous to use for the intended purpose. A specific example of the hazards inherent in this situation may be found in the case of insecticide space spray composed of 1% DDT, 0.1% pyrethrins, or 2.5% thiocyanate in deodorized kerosene and 5% residual-effect DDT, both of which are issued in 5-gallon steel drums. Obviously, if a requisition for residual-effect DDT were to be filled with space spray, the application of the solution as a residual-effect compound w ould be of little or no value. Under some conditions, when stocks have been exposed to such adverse weather conditions that all gross identifying marks have been removed from the containers, the assumption has been made by the untrained native laborers that all unidentifiable cans of the same size contained the same material. Were it possible to have just one insecticide for all military purposes, such a situation could easily be avoided. 

Additional materials and components that are normally included in a system satisfy safety needs, system performance indications, and common sense. Service switches should be placed within view of the fan to ensure that the system will not be activated while maintenance is in progress. Systems should be clearly marked as a radon reduction device to ensure that future owners of the building do not remove or destroy the system. An operation manual describing the system and its purpose should be made available. 

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