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Guide to Pressing Seaweed: Introduction
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Why would you want to press seaweed?
For a lot of reasons. Maybe to learn about the form and diversity of organisms, to make art, or to gain greater understanding of local coastal waters. People have been pressing plants for a long time, as scientific vouchers and as objects of curiosity and beauty. A visit to almost any natural history museum should give you some insight into the history of plant pressing, which had its heyday during Victorian times when proper ladies spent their days studying plants, bugs, and seaweeds (among other things). Whether approached in a casual or sophisticated way, pressing plants or seaweeds fosters education and appreciation. Why seaweeds? Because of their great beauty and diversity, and specifically because they aren't traditional emblems of beauty. Seaweeds offer an enormous palette of natural forms, colors, and textures, many of which are not found elsewhere. In many cases, these aesthetic characteristics reflect some of the interesting scientific characteristics of seaweeds, such as their great taxonomic, morphological, and functional diversity. In addition, in some ways seaweeds are a very practical subject to preserve by pressing: most are thin and stick naturally to paper.

What do you need to collect seaweed?
  • In some locations, a permit (You can freely collect seaweed along much of the United States; however, there are some locations where a permit is required. Check with local authorities before planning a collecting trip.)
  • Buckets and sealable plastic bags to hold and sort your seaweeds
  • Suitable shoes or boots (If collecting at a rocky shore, it is very important to have safe footing. Hip boots are ideal, as they have non-slip soles and are long enough to protect your legs from cold water and sharp rocks. Sandals, water shoes, rain boots, and rubber-soled sneakers provide good traction, but do little to support your ankles or protect your legs. Many people recommend against wearing chest waders, because they can be dangerous if they fill with water.)
  • Something to collect and transport seawater (plastic jugs or larger carboys are useful, and a cheap hand bilge pump will help a lot to fill them.)
  • Optionally, a small knife to help scrape seaweeds off of rocks and a long hook or net to help catch drift
  • A notebook to record information about the location where you are collecting
  • Towels, sunscreen, and enough clothing to protect yourself from the sun, heat, or cold
  • Ice packs to keep specimens cold when the weather is warm
  • Optionally, lightly tinted polarized sunglasses to help see into the water on sunny days

What do you need to press seaweed?
  • Fresh seaweed (Seaweed is best if pressed when first collected, but may be stored for a day or two in the cold in the dark [in a refrigerator]. Fine specimens should be kept in clean seawater, but coarse specimens are best kept in damp towels sealed in a plastic bag.)
  • Seawater (Best if cold, and filtered or clarified by decanting. Using seawater keeps your specimens alive and healthy. This is most important when pressing fine filamentous or membranous specimens, which can lose their color if put into tap water. Tap water can be used for some coarse specimens without a problem.)
  • Optionally, Formalin to preserve specimens before pressing (This is generally recommended by professionals and will help preserve the color and structure of some species; however, formaldehyde is toxic and noxious and should only be used in a laboratory setting.)
  • A tray or bucket in which to sort and clean your seaweed (light-colored plastic is best)
  • A shallow pressing tray (plastic cafeteria trays and photo-developing trays are ideal)
  • Optionally, a flat mesh rack to help lift your specimen and mounting paper out of the pressing tray (Cut to fit inside your tray, made of something that won't corrode in seawater, and with a mesh wide enough to easily drain the water, but small enough to support your wet paper. Perforated zinc sheeting, available at some hardware/DIY stores, is ideal, and can be trimmed with tin snips, filing off any sharp edges.)
  • Mounting paper (Medium- to heavy-weight art paper or herbarium paper cut to fit into your pressing tray; 100%-rag paper is best because it is archival and holds up well when soaking wet; standard-sized herbarium sheets are 11 16 inches [29 42 cm].)
  • Tools to help arrange your specimens (tweezers or forceps, small paintbrushes, toothpicks or dissecting needles, squirt bottles, basters, etc.)
  • Covering sheets of cheesecloth or any other material that can be used to prevent a specimen from sticking to the blotter above it in the press (waxed paper, muslin, mesh nylon stocking or other fine synthetic mesh fabric, nappy/diaper liners, etc.)
  • Blotting paper (blotter) or clean newsprint cut to the size of your press, or folded stacks of newspaper (100%-rag blotter is best)
  • Corrugated cardboard sheets (ventilators) cut to the size of your press, ideally with the flutes (corrugation) running parallel to the short length of the sheets (specialty corrugated aluminum ventilators are also available)
  • A plant press (Two rigid boards or lattice frames of equal size, used to dry plant specimens under pressure. Standard herbarium plant presses are 12 18 inches [30 46 cm], but presses can be any size.)
  • Weights, clamps, or straps to put your press under pressure (a stack of books or bricks will often suffice)
  • Herbarium tape or glue (Herbarium tape [neutral-pH gummed linen tape] is preferred for conservation purposes because it is relatively easy to remove, but may not be the first choice if aesthetics are a concern; clear-drying water-reversible glues like wheat paste are an alternative, and PVA or plain white glue [casein glue] is acceptable.)
  • Optionally, a fan (but not a pedestal fan) to help dry your specimens (very useful)
  • Herbarium labels (see an example here; ideally of 100%-rag paper)
  • A notebook, pencils, and pens (preferably with lightfast ink)
  • Field guides and taxonomic keys to identifying seaweeds
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