Opaque spots

Water Spray the plate to saturate Opaque spots appear on a translucent background. Not very sensitive and only applicable to preparative work... 

Figure 7 Types of defects commonly encountered on a process line, (l) contamination, (2) opaque spot, (3) large hole, (4) pin hole, (5) excess material, (6) lack of adhesion, (7) intrusion (mouse nip) and (8) scratch.

It is clear from this discussion that a solvent should be chosen which has the correct solution properties to yield a uniform film. The polymer should remain in solution throughout the entire spinning phase otherwise aggregation may occur which can lead to opaque spots, pinholes or irregular lines after development. 

Once a satisfactory film has been obtained, the coated substrate should be transferred to a suitable storage container and moved directly to the subsequent processing step, viz., prebaking. It is important that unbaked, freshly spun films not be stored for periods of time in excess of a few hours at this stage, since many resists are particularly vulnerable to particulate contamination. Once particles contact a resist surface prior to prebaking, they are almost impossible to remove and will cause opaque spots or pinholes after exposure and development. 

As in all processing steps, cleanliness of the exposure hardware is of paramount importance. Any particle that lands on the resist prior to exposure, will shield the film underneath the particle from the exposing radiation and give rise to opaque spots in the case of positive resist, or pinholes in the case of negative resists. Particulate contamination is especially troublesome with electron beam and ion beam systems where the probability of a particle landing on a substrate is increased relative to other techniques because of the much longer exposure times involved. 

Time-lapse photography has been used to follow the course of the suspension polymerization of vinyl chloride. This study showed that the spherical droplets of monomer burst under the action of the shearing force of the agitator to produce deformed and irregular resin particles. Without agitation, on the other hand, opaque spots appear in the spherical monomer droplets that increase in size as the polymerization proceeds [91]. 

In this application, the process analyzer is used in the vis-NIR spectral region to measure the clear top layer on a co-extruded polymer film. The bottom layer is pigmented to an opaque white color and its thickness cannot be determined by this method. Prior to the installation of the fiber-optic spectroscopy system, film samples were measured manually in the laboratory by a subtractive scheme. First, the total thickness of a sample was measured on a manual profilometer. The top layer of the polymer was removed with methylene chloride. The sample was then repositioned on the profilometer as closely as possible to the originally measured spot and the thickness of the second white layer was determined. The thickness of the top layer was then determined by difference. 

Several methods have been developed for quantifying dental fluorosis. The most commonly used method is Dean s index [49], which classifies fluorosis on a scale of 0 to 4 as follows class 0, no fluorosis class 1, very mild fluorosis (opaque white areas irregularly covering <25% of the tooth surface) class 2, mild fluorosis (white areas covering 25-50% of the tooth surface) class 3, moderate fluorosis (all surfaces affected, with some brown spots and marked wear on surfaces subject to attrition) and class 4, severe fluorosis (widespread brown stains and pitting). The average score of the two most severely affected teeth is used to derive the classification. Other commonly used methods to rate dental fluorosis include the Thylstrup-Fejerskov Index (TFI) [50] and the tooth surface... 

Night blindness (inability to see in dim light), conjunctival xerosis (dry and non-wettable conjunctiva), corneal xerosis (dry and non-wettable cornea and become opaque), keratomalacia (cornea becomes soft and burst open and vision is lost), Bitot s spots, growth retardation, dry and rough skin, sterility due to faulty spermatogenesis. 

Providing that care has been taken in the disc preparation the final disc should be slightly opaque due to the presence of the sample (the blank disc should be transparent). Should the disc show a number of white spots, it is probable that the mixture has been unevenly ground. If the disc shows a tendency to flake, then excessive grinding of the powder is indicated. If after being removed from the die the disc becomes cloudy this is indicative of the uptake of water to avoid this difficulty it is necessary to ensure that the die is evacuated for a sufficiently long period and that the removal of the disc from the die is carried out under a radiant heater. 

Jasper Prase (green), Plasma (dark green) Bloodstone, heliotrope Any color opaque most often red, green, brown and/or yellow, often multicolored Dark green with red spots or streaks... 

Bone Cream Opaque Warm Black spots Black lines Rigid Chalky-blue... 

Nanoseale manufacturing tool for drilling the fairly precise columnar penetration hole which is several microns in diameter, has been researched and developed. The laser beam with tightly focused spot and long focal depth can be used to process both transparent and opaque materials. The feature of the nanoseale measurement with an interferometer is an on-site measurement, and a dynamic control of the reference wave-front. 

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