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~1 D 4643 descnbed in this test method will m;nim;re its effects. Some microwave ovens have settings at less than full power, which can also be used to reduce overheating. 5.3 The behavior of a soil, when subjected to microwave energy, is dependent on its mineralogical compositions, and as a restdt no one procedure is applicable for all types of soil. Therefore, the procedure recommended in tfis test method is meant to serve es a guide when using the microwave oven. 5.4 This test method is best suited for minus No. 4 sized material. Larger size particles can be tested; however, care must be taken because of the increased chance of particle shattering. 5.5 The use of this method may not be appropriate when highly accurate results are required, or the test using the data is extremely sensitive to moisture variatiaos. 5.6 Due to the localized high temperatures drat the specimen is exposed to in microwave heating, the physical charatKetistics of the soil may be altered. Degregation of individual particles may occta, along wi0t vaporization ar chemical transition. It is Orerefore recommended that samples used is this test method not be used for otter tests subsequent to drying. Non I-Ile quality of the results produced try this test method is depe~mt m [he compe[mce of the penomel performing it and the suiubiliry of the equipment and facilities used Agmaes that meet the criteria of Practice D 3740 are gmaelly considered capable of competent end objecdve testing. Users of this test method ere cautioned that compliance with Practice D 3740 does not is itself costae reliable results. Reliable results depend on many factors; Practice D 3740 provides a means of evaluating some of those factors. 6. Apparatus 6.1 Microwave Oven-A microwave oven, preferably will a vented clamber, is suitable. The required size and power rating of tie oveo is dependent on its intended use. Ovens will variable power controls and input power ratings of about 700 W Lave be® found to be adequate for this use. Variable power controls are important and reduce the potential for overheating of the test specimen. Non 2-MiGOaeve ovens equipped with builo-in scales and compmer controls have been developed for use iv drying soils. Theo use is campatihle with this /rat method 6.2 Balances, having a capacity of 2000 g or greater and meeting the regt i~^°^'° of Specification D 4753 for a bala>Ke of 0.1 g readability. 6.3 Specimen Containers-Suitable containers made of a notunetallic nonabsorbent material, resistant to the[me] shock, and not subject to changes in mass or shape when subjected m repeated heating, woing, or cleaning. Porcelain evaporating [dishes sad standard borosilicate glass dishes perform satisfac- tarily. Other cantainets, stub as paper cups ar plates, also lave been used satisfactorily; however, [ley may require pre-drying prior to use. 6.4 Container Handling Apparatus-A glove or folder, suitable for removing for containers from rite oven. 6.5 Desiccator-A desiccator cabinet orjar of suitable size containing silica gel, anfydrous calcium phosphate, or equiva- lent. It is preferable to trse a desiccant tfat changes color to indicate tLat it nceds reconstitution. 6.6 Heat Sink-A material or liquid placed in rite micro- wave to absorb energy after the moisture has been driven from the test specimen. The heat sink reduces the possibility of overheating the specimen and damage to the oven. Glass beakers filled with water end materials that have a boiling point above water, such as nottfiammable oils, have ban used successfully. Moistened bricks Lave also been used. 6.7 Stirring Tools-Spatulas, putty knives, and glass rods for cutting and stirring the test specimen before and during the test Short lengths of glass tads have been found useful for slitting and may be left m the specimen container during testing, reducing the possibility of specimen loss due to adhesion to tfe storing tool. 7. Hazards 7.l FIandle hot containers with a container holder. Some soli types can retain considerable feat, and serious bums could result from improper Candling. 7.2 Suitable eye protection is recommended due to the possibility of particle shattering during Ute heating, mixing, or mass d~~_;~:tions. 7.3 Safety precautions supplied by the manufacturer of the microwave should be observed. Particulm atantion should be paid to keeping the door sealing gasket and door interlocks clean and in good working condition. Non 3-The vu of a mitmwave oven for the dryivg of mils may be considered abutive by the tnaatrfactures and crosimte voiding of war- tanties. IrLaowave drying of mils containing me®llic materiels may uvx arcing in the Quin. Highly organic mils and sods containing oils end coal may ignite and bran riming microwave drying. Continued opaadon of the oven after the mil has reached wnsunt weight may elm cause damage oc premature failwe of the tnimaweve Quin. Non 4-Whea fast inaoduced. micoweve oven were reported [o affect hewn pacemakers, primarily beaux of du operating 6equrncin of the two devices. Since that time, pacemaker have hem raiesigoed, and the microwave oven is rot regarded as the health Itarard it ovice was. However, it may be advisable m post warnings that a microwave is in ux. 7.4 Flighly organic soils a~ soils containing oil or other contaminates may ignite into flames during microwave drying. Means far smothering Names to prevent operator injury or ovrn damage should be available during testing. Fumes given off from contaminated soils or wastes may be toxic, and tfc oven should be veined accordingly. 7.5 Due to the passibility of steam explosions, or Otermal stress shattering porous or briu]e aggregates, a coveting over the sample container may be appropriate W prevent operator injury or oven damage. A cover of heavy paper toweling has beat fotrnd satisfactory for this purpose. This also prevenu scattering of the test sample in the oven during the drying cycle. 7.6 Do not use metallic containers in a microwave oven becatrse erring and oven damage may result 7.7 Observe manufacturer's operating instructions wfen installing and using the oven. 7.8 The placement of the test specim® duectly on the glass liner tray provided with some ovens is strongly tiiscotnaged. The conce~ated heating of the specimen may result in the gl~ ~Y slm~g, Possibly causing injury to the operator. 8. Samples S.l Keep the samples that are stored prior to testing in