Absorbent.\u00a0 A term applied to papers that absorb water solutions or other liquids. Examples of absorbent papers are blotting and toweling products. Many mat boards tend to have absorbent properties. Acid burn.\u00a0Paper, glue, tape and related products contain acid. When materials that contain acid come into contact with a photograph or artwork, the acids can leach into the photo and cause acid burn \u2013 where the photo paper to become brittle and yellowed. Acid-free.\u00a0There are specialty paper and craft products designed for archiving and framing purposes. Acid-free materials have, at the very least, the lowest allowable amount of acidity so that it does not cause any damage. These are paper materials that contain a pH value between 6.5 to 8.5. Acrylic.\u00a0This is a type of glazing that can replace real glass in picture frames. Also called plexiglass, acrylic is lighter and more resistant to breaking. Acrylic can also come with UV protective and anti-glare properties. Adhesive Coated Board. A board with an adhesive coating on one side that may be neat-activated or pressure sensitive. Allowance.\u00a0This provides extra space in the widths and lengths of the frame to make sure that all the items that go into the frame (the photo, matting, mounting boards, backing and glazing) will have an excellent fit. The allowance provides space for the expansion of the paper-based materials as they expand and contract to changes in the temperature and to humidity. The allowance is usually 1\/8 inch for both the width and the length of the frame. Antiquing.\u00a0This is a process that enables one to mimic the look of an\u00a0antique picture frame. Antiquing can involve the use of a buffing chemical, scratching and painting. Archival framing.\u00a0This is a type of framing philosophy that aims towards protecting and preserving the photo. With archival framing, only materials that are acid-free should come in contact with the photo. The mounting techniques employed are also reversible, meaning the photo can be removed from the frame without causing any damage to it. Backing.\u00a0Also called the mounting board, this is where the photo is attached before it is placed inside the frame. The backing works to keep the photo in place and to prevent the photo from creasing and warping. Beveled edge.\u00a0This refers to a slope at the edge of the frame and mat board. For the mat board, the slope rises from the inside to the outside, exposing the core of the mat board. This creates another line around the photo\u2019s edges, adding visual impact and drawing the eye into the photo. Cardstock.\u00a0This is specialized craft paper that is thicker and stiffer. This can serve as the backing of the photograph to prevent it from buckling. Contemporary style.\u00a0This pertains to the design and finishing of the frame. A contemporary picture frame will usually have simple, clean lines accompanied by the use of natural wood grains or a shiny metallic finish. Convex glass.\u00a0This is curved glass that was used in the early 1970\u2019s for antique portraits. The curvature of the\u00a0convex glass\u00a0serves to minimize contact between the photo and the glass so that if moisture gets inside the frame, the photo will not stick to the glass. Convex glass is also known as \u201cbubble glass\u201d. Double mat.\u00a0For added effect, matting is added to the photo. There are times when two matting boards are used to add to the color contrast and to further accent the photo. Two layers of matting are placed one to top of the other. The top one has a smaller opening than the lower matting, allowing just a part of the bottom matting to show. The double matting serves to provide a sense of depth to the photo. Enamel.\u00a0For wood frames, an extra layer of enamel is added to the wood for aesthetics and protective purposes. Enamel can be semi-transparent or opaque. Foam core.\u00a0This is an acid-free and conservation friendly backing alternative to cardstock. This is light but strong enough to hold the photo. Frame size.\u00a0When buying a picture frame online and choosing a frame based on frame size, remember that this refers to the frame\u2019s inside opening and\u00a0not\u00a0the outer edges of the frame. When computing for the right frame size, consider the largest opening you will need to reveal the photo or the outermost matting, if any. To illustrate, a 6 x 8-inch photo that has matting with a 2-inch width will need an 8 x 10-inch frame size. Glazing.\u00a0This is the transparent layer of glass or acrylic that covers the top of the picture. The glazing serves to protect the photo against the elements. Glazing can also UV protection and anti-glare capabilities. Gilding.\u00a0A picture frame\u2019s look can be further enhanced by adding a layer of gold or silver powder or leaf (very thin, flat sheets) on the layer of the frame\u2019s molding. Hinging.\u00a0This is one way of attaching a photo on to the mounting board. This involves the use of adhesive strips or tape in a way that the tape is not visible and the photo hangs free to expand and contract as it reacts to humidity and temperature. Jersey frame.\u00a0This is a specialized\u00a0display case\u00a0that is designed to showcase a sports jersey. Lignin.\u00a0Commonly found in printing papers, this polymer is derived from wood. Over time, the lignin in paper can form acids. If there is a photograph in contact with a paper that contains lignin, the acids will cause damage to the photo. Lip.\u00a0This refers to the picture frame\u2019s inner edge. The lip prevents the glazing and other components of the frame from falling out. The lip also serves to hide the rabbet. The lip can be beveled or ornamented. Matting.\u00a0This layer of board comes with a frame opening that offers the viewer a \u201cframe within a frame\u201d. The matting board also works to keep the photo from coming into contact with the glass. Molding.\u00a0This comprises the visible and decorative part of the picture frame. The molding also holds the basic structure of the frame. Non-invasive mounting.\u00a0This refers to any reversible process of attaching the photo to the mounting board. With this, a photo can be easily removed from the frame without damaging it. Some non-invasive mounting methods include the use of adhesive photo corners and hinging techniques. Ornamentation.\u00a0This refers to the decorations on the picture frame molding. Some examples of ornamentation are beading, medallions and flower-and-leaf designs. Pressure-sensitive tape.\u00a0This adhesive tape does not need chemicals or heat for it to stick to a surface. This only needs pressure applied by hand for the tape to adhere. Rabbet.\u00a0This is the space under the inner lip that holds the glazing, matting, picture, mounting board and backing. When purchasing a picture frame online, take note of the rabbet depth to ensure that all the components fit inside the frame. Reverse molding.\u00a0With this type of molding design, the inner lip has the highest part of the frame molding. This can add a sense of depth to the photo but care has to be given to ensure that the design does not detract from the photo. Shadow box frame.\u00a0This is a specialized display case, very similar to a picture frame but with an extra depth. With this, the frame can accommodate 3-dimensional items. Spacer.\u00a0These are thin and clear plastic strips that add some space between the photo and the glass. This is placed on the lips of the frame. The gap the spacers make enable any moisture that comes into the frame to dry out without causing any damage to the photo. UV Rays.\u00a0The sun\u2019s (and even artificial light\u2019s) ultraviolet rays can cause damage to the photo, causing the photo to become brittle and faded. To prevent this, choose a glazing with UV protection. Weighting.\u00a0To add more drama to matting, one can have a matting board with a bottom that is wider that the other three sides.