How to check wood moisture content with a multimeter. Methods for determining wood moisture content. How to measure wood moisture content scientifically

Determining wood moisture content

To determine the moisture content of wood, you can use one of two methods. Used in everyday life special devices– electric moisture meters. The device works on the principle of changing the electrical conductivity of wood (changes with humidity). Electric moisture meter needles, with wires connected, are inserted into the tree and passed through it electricity, at this moment on the scale of the device you can see the degree of moisture in the wood in the place where the measurement is being taken.

Some carvers with extensive experience can determine the moisture content of wood by eye. Also, knowing the density and other physical properties different types wood - you can determine its moisture content by mass, if there are cracks along the fibers or at the end - by warping. By the color of the wood, the color of the bark and its size, freshly cut or ripe wood is determined, as well as its moisture content.

If, when processing wood with a plane, the chips are easily compressed by hand, the material is wet, but if, when compressed, the chips crumble and break, the material is quite dry. You also need to pay attention when making transverse cuts with chisels: if a wooden piece crumbles, the material is too dry.

A piece of wood, which is very easy to cut, is very wet, and a wet mark will be noticeable at the cut site. Note that it is quite difficult to obtain high-quality wood blanks, since warping, cracking and other deformations during drying cannot be avoided.

Drying wood

Dry wood is stronger, more durable, better finished, easily glued, does not rot, and does not warp so much. Any wood, regardless of its species, subtly senses changes in the humidity of its environment. This property is one of the most important disadvantages of timber. In warm and heated rooms it warps and dries out, and at high humidity it very quickly absorbs water and begins to swell. The optimal moisture content of wood outdoors is 18%, and indoors – up to 10%.

Today there are many various methods drying wood. The most accessible and simplest type of drying is air (atmospheric). Drying should take place in the shade, in a draft and under a canopy. When dried in the sun, the surface quickly heats up and dries out, but inner part the workpiece remains damp. As a result, cracks appear (due to stress differences).

Beams, boards and other p/m must be stacked on wooden, metal or other supports with a height of 50 cm. Boards must be laid with the inner faces towards the top to avoid warping.

If the boards are placed on the edges when drying, the process will be faster, since there will be better ventilation and, accordingly, the moisture will evaporate faster. However, there is a significant drawback - the boards warp more, especially with high humidity. When harvesting live and freshly cut trees, after laying it is necessary to compact them with a heavy load to avoid severe warping.

During natural drying, cracks will always form at the ends. To avoid cracking of the ends, they must be well painted with oil paint or impregnated with bitumen or hot drying oil, this will protect the pores of the wood. Processing of the ends must be carried out immediately after cross-cutting into the section. If the wood is very damp, dry the ends with a blowtorch and then begin painting.

The ridges (trunks) must be cleared of bark (barked), only at the ends there should be collars up to 25 cm wide to avoid cracking. Peeling the bark is necessary to speed up drying and protect against beetles. Wood left with bark in a warm room and with a high level of humidity will very quickly begin to rot and become affected by fungi.

After drying by atmospheric method in warm weather, the wood moisture content will be from 12 to 18%.

There are other ways to dry wood.

Evaporation method

Evaporation (steaming) has been used since ancient times. The blanks were sawed into pieces, taking into account the size of the product, then ordinary cast iron was laid and sawdust from the same wood was added, filled with water and left in a heated and cooling oven at a temperature of 60-70 degrees. As a result of such actions, the process of “leaching” (evaporation of wood) occurs - the workpiece loses all its natural juices, is colored and takes on thick chocolate shades, with a rather pronounced natural pattern. Such a workpiece is easier to process, and after drying - there will be much less warping and cracking.

Waxing method

The wooden blank is dipped into a paraffin solution and left in the oven for several hours at a temperature of 40 degrees. Next, the wood is allowed to dry for several days, as a result of which it has the same properties as after steaming: a tinted surface with a clear texture pattern, does not warp or crack.

Method of locking in linseed oil

Dishes made from wood steamed in linseed oil are waterproof and practically do not crack even with everyday use. This method is still used today. The workpiece is placed in a container, poured linseed oil and steam over low heat.

Wood is a natural material that is quite susceptible to moisture. It is capable of releasing and absorbing moisture depending on environmental conditions. When the microclimate remains unchanged, the wood moisture content tends to remain constant.

Determining wood moisture content largely depends on the type of wood. The most hygroscopic are pear, beech, and kempas. The most resistant are oak, bamboo, and merbau.

The use of wood for construction and renovation requires compliance with humidity standards. The term “moisture content” refers to the percentage of water to dry wood.

Humidity types

There are two types of humidity of wood raw materials: relative and absolute.

Absolute

This concept is characterized by the ratio of the mass fraction of moisture of a certain volume of wood to the weight of absolutely dry raw materials of the same size. There are established state standards for this indicator. According to them, the indicators of the absolute humidity meter of the board should be within 9%.

Relative

This is the percentage of moisture contained in the wood to the mass of wet wood. In wood raw materials, water is found in two forms: free and bound. They indicate the total amount of moisture in the raw material. The volume of bound moisture depends on the microclimate, as it is absorbed from the air. It is located in the cellular structure of the tree. It is because of this, depending on the humidity environment, swelling or shrinkage of the material occurs. Bound water can only be removed by drying.

Free moisture does not lead to swelling, since the water in this case is in the intercellular structure of the wood. But thanks to it, the density of the material increases.

In addition, the type of wood raw material depends on the degree of its moisture content.

There are several types of wood moisture content:

Wet. This category includes wood that has been exposed to water for a long time. In this case, the humidity meter reading is more than 100%.

Freshly cut. The moisture content of a recently felled tree is between 50-100%.

Room dry. This type of material has been in a heated building for a long time. Therefore, its number is in the range of 9–13%.

Air dry. This type of wood is long time was stored in the fresh air. Depending on environmental conditions, its indicator is in the range of 15–20%.

Absolutely dry. Such indicators can only be achieved by drying in a special device. The amount of water in this case is 0.

How to find out the moisture content of wood?

There are several methods for determining wood moisture content. But first you need to find out the type of plant and air moisture, since for different trees there are standards.

In order to measure the moisture of wood raw materials, as a rule, two methods are used: gravimetric or using an electrical device. Their indicators may differ slightly, but not significantly.

Weight

For this method you will need:

very accurate scales;

Measuring process:

To begin with, you need to cut off a piece 10–15 millimeters wide from the middle of the board with your own hands. It will serve as a control sample. The main thing at this stage is to take the block from the center of the board. There is no need to cut off the end part, as it has much less moisture.

After weighing, this piece must be sent to a special dryer, a device with a temperature of about 100C°.

The first weighing is done by hand after five hours. All subsequent indicators are recorded at intervals of 1–2 hours.

Drying is carried out until the weight indicator begins to repeat. This means that the material has become completely dry. Let us denote the numerical indicator of the last sample as “Pc”.

W = (Ph-Pc) : (Pc x 100%)

W – percentage indicator; Ph – first weight; Pc – final weight.

To get more reliable results, it is better to use two sample samples.

Electric

It takes a lot of time to carry out weight measurements of wood. On average, this work takes about nine hours. But there is a way that allows you to determine the percentage of water in a tree much faster and more accurately.

It is much easier to determine the moisture content of wood raw materials using an electric moisture meter.

The operating principle of a moisture meter is based on a change in the electrical resistivity of a material depending on its humidity.

The needle-electrodes of this device are inserted into the wood so that they are opposite each other. A current is passed through them, and the moisture meter shows the amount of water in this section of the tree. But since the moisture meter measures moisture only locally, it is better to repeat the measurement in several places.

How to determine the moisture content of wood without technical means?

Today, the amount of water in wood raw materials is determined using complex calculations and the latest instruments. But people have always been involved in construction. And somehow they managed without progressive methods and moisture meters.

It is necessary to draw a line along the freshly cut fragment with a pencil. When the wood is wet, the line will turn blue after a while; if it is dry, it will not.

The shavings can “tell” about the amount of water in wood raw materials. If they are elastic, soft, and do not break when crushed, the tree is wet. Shavings of dry raw materials in your hand will break and crumble.

You can run a sharp metal object over the wood with your own hands. The condition of the material is determined by the trace left behind. A wet tree will have a wet mark.

You can determine the amount of moisture in wood raw materials by hitting it with a wooden object. If the sound is dull, the wood is wet; if the sound is thin and ringing, the wood is dry.

The dryness of the wood is also indicated by cracks at its ends. Wet material has fewer of them. When moisture seeps into the hole when sawing a board with your own hands, the wood contains a large number of

water and unsuitable for work. Too dry raw materials crumble during such processing. Wood moisture plays a huge role in construction and renovation. raw wood

It will become deformed during the drying process. To avoid this, you should only work with dry material.

Wood is an affordable, environmentally friendly material, widely used in the construction and decoration of buildings. However, many refuse it for the reason that over time the wood begins to warp and cracks appear in the structures. This happens as the wood dries. This problem can be avoided if you work with dry material. The moisture content of lumber is regulated by a number of documents, in particular SNiP II-25-80.

But how can you find out the moisture content of wood when purchasing? It is quite difficult to determine this by eye. Only a specialist with extensive experience can determine by certain signs whether the wood is wet or dry, but he will not give an exact percentage. Some conclusions about moisture can be drawn when processing lumber. If the shavings removed by a plane are plastic and bend, then the wood is damp; if it crumbles, it is dry. Construction regulations require an exact figure, and to determine it there are a number of methods, the most used of which are calculation by mass and calculation using a special device - a moisture meter.

Calculation of wood moisture content by mass

Figure 1. Density table various types wood.

It is known that different tree species have different densities. But the density depends not only on the species, but also on the moisture content of the lumber: the drier the wood, the lighter it is. Data on the most common rocks are presented in the table in Figure 1. Knowing the volume and mass, you can calculate the density, find it in the table for of this tree and thus determine the moisture content of the wood. It's quite simple and quick way determination of humidity. However, it should be taken into account that the density of trees even of the same species, but growing in different climatic zones, may vary, so errors in calculations cannot be avoided.

To more accurately determine the moisture content of lumber, a study is carried out. For testing, a sample measuring 20x20x30 mm is taken. The sample is cut from the lumber at a distance of at least 30-50 cm from the edge of the board. It is weighed on a scale with an accuracy of 0.1 g and placed in drying cabinet with a temperature of 101-104 ° C. After 6 hours, the sample is taken out of the cabinet, re-weighed and put back in the cabinet. Subsequent weighings are carried out at intervals of 2 hours. The weighing results are recorded in a journal. If the difference in mass based on the results of two weighings does not exceed 0.1 g, then the wood is considered absolutely dry.

Calculation of wood moisture content.

The absolute humidity of the material is calculated using the formula:

W=(m-m0)/m0×100(%),

where W is the humidity, m is the mass of the sample at the first weighing, m0 is the mass of the same sample after complete drying.

It is necessary to consider how to determine the moisture content of a sample using an example. We can assume that before drying it weighed 98.76 g, after drying - 65.81 g. Then W = (98.76-65.81)/65.81x100 = 50.1%.

To obtain a reliable result, it is necessary to conduct a study with several samples. It is not recommended to keep resinous rock samples in a drying cabinet for more than 20 hours.

This method of determining wood moisture content complies with GOST 16483.7-71, but it takes a lot of time and requires special laboratory equipment.

Determining humidity using a moisture meter

A moisture meter can be used to determine the moisture content of wood.

Scientific and technological progress, manifested in all spheres of human activity, has not stood aside in relation to such an issue as determining the moisture content of wood. Today, a moisture meter will not surprise anyone. The cost of this portable device depends on the manufacturer, model and set of functions, but it is not so high that you can refuse it convenient device. Moisture meters are available in almost any warehouse where lumber is stored or sold. And therefore, measuring humidity turns into a matter of minutes.

The principle of operation of a moisture meter is based on measuring resistance when an electric current is passed through wood. The device has needle sensors that are buried into the lumber along the grain. When you press the measurement button, a current is passed through them, and the result, already converted into a humidity indicator, is instantly displayed on the display. The measurement error of modern moisture meters is no more than 1.5%. It should be understood that the result is reliable only for the place where the needles are deepened. To judge the condition of the lumber as a whole, it is necessary to take as many measurements as possible along the entire length and width of the board.

Acceptable wood moisture content according to GOST.

A number of models have a long conductor connecting the device to needle sensors. This allows you to measure the moisture content of wood remotely while drying it in the chamber. In this case, sensors are inserted into boards located in the middle of the stack. The device itself is placed outside the chamber. When taking measurements, it is necessary to make corrections for temperature. Remote method is convenient for controlling the wood drying process, but it should be recognized that it often gives distorted results. This happens for two reasons: due to heating of the sensor needles, which transfer it to the wood in places of deepening, and due to the violation of the tight contact of the sensors due to drying of the wood.

In cases where even minimal damage to wood is extremely undesirable, for example, when it comes to furniture parts, the moisture content of wood can be determined using a non-contact moisture meter.

It does not have needles, but is simply applied to the surface of the lumber. The operating principle of the device is based on measuring the length of electromagnetic waves, which will differ depending on humidity. When measuring with such a moisture meter, the wood should be determined by its species.

Drying wood

Damp wood is not a death sentence. It is quite possible to bring it to a workable state even without drying it in a chamber. Moreover, atmospheric drying is recommended for any purchased lumber. Drying wood comes down to its proper storage. To do this, set up a place in a draft, protected by a canopy from precipitation and direct exposure. sun rays

. The last condition is due to the fact that under the sun the surface of the boards quickly heats up and dries, while the bottom remains wet. Because of this, tension arises, the wood warps and cracks. Logs with a height of at least 0.5 m from the ground level are installed under the stacks. The surface of the base must have a strictly horizontal orientation. To avoid sagging of the boards, the distance between the support points should not exceed 1.5 m. Between the rows of boards, spacer boards made of coniferous species 25-40 mm thick, and after 1.0-1.5 m - gaskets 100-150 mm thick. This will ensure better air circulation. You cannot stack boards that have different humidity

: Wood is hygroscopic, and dry lumber will pick up moisture from wet lumber.

The time required for drying to 18-22% moisture varies from 9 to 40 days. It depends on climatic conditions, time of year and thickness of the material. The tree is natural material

, very susceptible to fluctuations in temperature and humidity. The main property of wood is hygroscopicity, that is, the ability to change humidity in accordance with environmental conditions. They say that wood “breathes,” that is, it absorbs air vapor (sorption) or releases it (desorption), responding to changes in the microclimate of the room.

Measuring wood moisture content with a moisture meter

The ability to absorb moisture is affected not only by the microclimate of the room, but also by the type of wood. The most hygroscopic species include beech, pear, and kempas. They respond most quickly to changes in humidity levels. In contrast, there are stable species, for example, oak, merbau, etc. These include the bamboo stem, which is very resistant to unfavorable climatic conditions. It can even be installed in the bathroom.
Different types of wood have different moisture levels. For example, birch, hornbeam, maple, and ash have low humidity (up to 15%) and, when dry, tend to form cracks. The moisture content of oak and walnut is moderate (up to 20%). They are relatively resistant to cracking and dry less quickly. Alder is one of the most drying-resistant species. Its humidity is 30%.

Humidity- one of the main characteristics of wood. The moisture content of wood is understood as the percentage ratio of the mass of water to the dry mass of wood.

Absolute humidity of wood is the ratio of the mass of moisture contained in a given volume of wood to the mass of absolutely dry wood. According to GOST, the absolute humidity of parquet should be 9% (+/- 3%).

Relative humidity wood- this is the ratio of the mass of moisture contained in wood to the mass of wood in a wet state.

There are two forms of water found in wood - bound and free. These add up to the total amount of moisture in the wood.

Bound (or hygroscopic) moisture is contained in the cell walls of wood, and free moisture occupies the cells and intercellular spaces.

Free water is removed more easily than bound water and has less effect on the properties of wood.
According to the degree of moisture content, wood is divided into the following types:

Wet wood
Its humidity is more than 100%. This is only possible if the wood has been in water for a long time.

Freshly cut
Its humidity ranges from 50 to 100%.

Air dry
Such wood is usually stored in air for a long time. Its humidity can be 15-20%, depending on climatic conditions and time of year.

Room-dried wood
Its humidity is usually 8-10%.

Absolutely dry
Its humidity is 0%.

During prolonged drying, water evaporates from the wood, which can lead to significant deformation of the material. The process of moisture loss continues until the moisture level in the wood reaches a certain limit, which directly depends on the temperature and humidity of the surrounding air. A similar process occurs during sorption, that is, absorption of moisture. A decrease in the linear volume of wood when bound moisture is removed from it is called shrinkage. Removing free moisture does not cause shrinkage.

Shrinkage varies different directions. On average, complete linear shrinkage in the tangential direction is 6-10%, and in the radial direction - 3.5%. With complete drying (that is, one in which all bound moisture is removed), the moisture content of the wood is reduced to the limit of hygroscopicity, that is, to 0%. If moisture is unevenly distributed during drying of wood, internal stresses can form in it, that is, stresses that arise without the participation of external forces. Internal stresses can cause changes in the size and shape of parts during mechanical processing of wood.

The properties of wood directly determine the properties of wooden products. When there is excess or insufficient moisture, wood usually absorbs or releases moisture, increasing or decreasing in volume accordingly. With high humidity in the room, wood can swell, and with a lack of moisture, it usually dries out, so everything wooden crafts, including floor coverings, require careful maintenance.

To prevent deformation of the floor covering in the room, it is necessary to maintain constant temperature and humidity. This has a beneficial effect not only on quality and durability floor coverings And wooden furniture, but also on people's health. With a sharp change in the temperature and humidity conditions in a room, internal stresses arise in the wood, which lead to cracks and deformations.

The optimal temperature in a room with parquet flooring should be approximately 200C, and optimal humidity air - 40-60%. Hydrometers are used to monitor room temperature, and room relative humidity is maintained using humidifiers.

DETERMINATION OF WOOD MOISTURE

There are several ways to determine wood moisture content. IN living conditions use a special device - an electric moisture meter. The operation of the device is based on changes in the electrical conductivity of wood depending on its humidity. The needles of an electric moisture meter with electrical wires connected to them are inserted into the wood and an electric current is passed through them, while the moisture content of the wood is immediately marked on the scale of the device in the place where the needles are inserted.

Many experienced carvers determine the moisture content of wood by eye. Knowing the types of wood, its density and other physical properties, it is possible to determine the moisture content of wood by mass, by the presence of cracks at the end or along the wood fibers, by warping and other signs.

By the color of the bark, its size and the color of the wood, you can recognize ripe or freshly cut wood and the degree of its moisture content. When processing a semi-finished plane with a plane, its thin shavings, compressed by hand, are easily crushed, which means the material is wet. If the chips break and crumble, this indicates that the material is dry enough.

When making transverse cuts with sharp chisels, also pay attention to the shavings. If they crumble or the wood of the workpiece itself crumbles, this means that the material is too dry. Very wet wood is easy to cut, and a wet mark from the chisel is noticeable at the cutting site. But in the end it is unlikely that it will be possible to obtain a high-quality thread, since cracking, warping and other deformations cannot be avoided.

DRYING WOOD

Wood drying is the process of removing moisture from wood to a certain percentage of humidity.
Dry wood has high strength, warps less, is not susceptible to rotting, is easy to glue, is better finished, and is more durable. Any wood of various species reacts very sensitively to changes in environmental humidity. This property is one of the disadvantages of timber.

At high humidity, wood easily absorbs water and swells, but in heated rooms it dries out and warps. Indoors, wood moisture content is sufficient up to 10%, and outdoors - no more than 18%. There are many ways to dry wood. The simplest and most accessible type of drying is natural - atmospheric, airy. Wood should be dried in the shade, under a canopy and in a draft.

When dried in the sun, the outer surface of the wood quickly heats up, but the inner surface remains damp. Due to the difference in stress, cracks form and the wood quickly warps. Boards, timber, etc. are stacked on metal, wooden or other supports with a height of at least 50 cm. The boards are stacked with their inner layers facing up to reduce their warping.

It is believed that boards placed on the edges dry faster, since they are better ventilated and moisture evaporates more intensely, but they also warp more, especially material with high humidity. It is recommended to compact a stack of p/m, prepared from freshly cut and live trees, with a heavy load on top to reduce warping.

During natural drying, cracks always form at the ends; to prevent cracking and preserve the quality, it is recommended to carefully paint the ends of the boards oil paint or soak in hot drying oil or bitumen to protect the pores of the wood. The ends must be processed immediately after cross-cutting into the cut.

If the wood is characterized by high humidity, then the end is dried with a flame. blowtorch, and only then paint over it. The trunks (ridges) must be debarked (cleared of bark), only small collars-muffs 20-25 cm wide are left at the ends to prevent cracking. The bark is cleaned so that the tree dries out faster and is not affected by beetles.

A trunk left in the bark in relative heat with high humidity quickly rots and is affected by fungal diseases. After atmospheric drying in warm weather, the wood moisture content is 12-18%.

Wood drying methods

Evaporation method Or steaming has been used in Rus' since ancient times. The blanks are cut into pieces, taking into account the size of the future product, placed in ordinary cast iron, sawdust from the same blank is added, filled with water and placed for several hours in a heated and cooled Russian oven “languishes” at t = 60-700C. In this case, “leaching” occurs - evaporation of wood; Natural juices come out of the workpiece, the wood is painted, acquiring a warm, thick chocolate color, with a pronounced natural texture pattern. Such a workpiece is easier to process, and after drying is less likely to crack and warp.

Waxing method The blanks are dipped into melted paraffin and placed in an oven at t=400C for several hours. Then the wood dries for a few more days and acquires the same properties as after steaming: it does not crack, does not warp, the surface becomes tinted with a distinct texture pattern.

Method of steaming in linseed oil Wooden dishes steamed in linseed oil are very waterproof and do not crack even with everyday use. This method is still acceptable today. The workpiece is placed in a container, filled with linseed oil and steamed over low heat.

When buying lumber for construction or the manufacture of furniture, windows or other products, many want to receive high-quality and reliable material. But often purchased wood turns out to be under-dried, which as a result leads to its cracking, deformation or damage due to the development of the rotting process.

The question of how to check the moisture content of wood is relevant and remains so. Moisture meters are mainly used to measure humidity. Both industrial and household use. Below is a table showing the density different varieties wood. And then, let's look at the technique of how to determine the moisture content of wood without a moisture meter in 2 ways.

How to determine wood moisture content without a moisture meter?

For those who do not know how to determine the moisture content of wood, you can use special tables. From them, knowing the type of wood, you can determine its density. These tables summarize indicators obtained as a result of laboratory studies using special diagnostic research equipment.

Knowing that each type of wood is unique in structure, weight and density, and using tabular data, you can determine the moisture content of a particular sample in field conditions. Which is important for further heat treatment.

Below we will consider how to determine the moisture content of wood, based on tabular values and using simple measurements:

The first step is to measure the mass and volume of the sample. These manipulations are performed in the usual ways using the simplest devices.
The density of the material is calculated using formulas. In this case, it is necessary to remember about the error, which in any case will arise due to the difference in the places where the trees grow. In some it is greater, in others it is lower.

In addition, humidity may vary depending on different parts tree. For example, in the trunk it is about 50% for pine and 60% for spruce. The branches, being less massive, and due to regular airflow, contain no more than 56 for pine, and 46 for spruce.

The tops of trees contain up to 60% moisture, and the bark accumulates from 36 to 67. Taking into account all these indicators, it is necessary to determine the average for all parts of the tree in order to further use the obtained value in calculating intermediate values.

Undoubtedly, the most important indicator in construction using lumber is the moisture content of the wood; the methods for determining it involve taking certain measurements. The first step is to determine the absolute humidity. As practice shows, this is more of a theoretical indicator that reflects the amount of water in the remaining volume of wood. It is determined by the following formula:

The next step is to determine the moisture content of the wood at the time of testing, taking into account the calculated relative humidity. Calculations are carried out using the following formula:

In addition to the types of moisture described above, there are also 2 types of moisture found in the thickness of wood. These include free moisture and bound moisture. In the first case, water is located in the cell cavities and intercellular space. Bound moisture is located inside the cell walls, making it difficult to remove from them and remaining inside.

A dry board differs from a wet board:

weight,
color,
smell,
ringing - if you hit it

How to measure wood moisture content scientifically?

There is also a second way to find out humidity. It is about research prototype dimensions 20x20x30 mm. In this case, the sample is taken not from the very edge, but further from it at a distance of 30-50 cm. As a rule, in this zone it is maximum and was not subject to natural evaporation.

To measure the moisture content of wood, the gravimetric method is used; the cut sample is weighed on a scale with high accuracy. At the next stage, the sample is placed in a drying cabinet, in which the temperature is maintained at 101-104 degrees. The heat treatment procedure continues for 6 hours. The sample is then removed and weighed again and returned to the cabinet.

The results obtained in this way are entered into a summary table. If the second measurement leads to a similar result from the first case, then the wood is considered completely dry.