av Angus Maciomhair » 21 november 2003, 10:45
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Joakim K</i>
Ben och hudlim är nog helt klar de mest använda. Nuförtiden är det dock betydligt enklare att få tag i mjölk...
Hur blir resultatet jämfört med ben och liknande?
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Som tidigare lovat kommer här en jämförelse mellan olika sorters lim (om än något grov) hämtad från <i>Traditional Bowyers’ Bible, vol. 1 </i> sid. 204-6.
Översättningen till svenska lämnas som en övning åt intresserade läsare.
A do-at-home glue strength test:
”This test is fairly crude, but within an accuracy of 10% or so, it will let you compare the relative strengths of different types of glue, and of different ’cookings’ of animal glue. … Rock or sugar maple was used in this test because it is a non-ring-porous, strong and widely available. Samples are cut into one-inch squares, ½” thick. … Glue two squares together … Let dry, or set, for recommended times.
Scrape or file surplus glue from the sample’s edge to reveal a clean, distinct glue line. Excess glue will throw readings off. Chisel a 1” square hole into a hickory baseboard, another 1” hole into a hickory wrench … The sample is set into a square socket so it can be gripped on all four sides. When held on only two sides in a vice the wood fails before even medium strength glue fails.
Set one side of the two-square sample in its base socket, and place the hikory wrench on the other square. Maintain about a 1/8” gap between the base and wrench, with the glue line in between. Position a spring scale ½” from the wrench end, keeping the scale at 90 degrees. Pull until either glue or wood fails, noting poundage at the moment of failure.”
*Candle wax ……………. ………………1 lb
*Double stick tape……………………….1 lb
*Contact cement…………………………3 lb
*Cottage cheese alone, clamped…………4 lb
*Powdered skim milk & lime paste……...5 lb
*Pine pitch……………………………….6 lb
*Ice……………………………………….9 lb
*Duco ™ ”airplane cement”……………10 lb
*Curds & lime…………………………..16 lb
*Commersial casein……………………..18 lb
*Urea resin………………………………18 lb
*Cottage cheese & lime…………………20 lb
*Epoxy putty ……………………………23 lb
*Resorcinol ™…………………………..25 lb
*White glue on unsurfaced wood……… .25 lb
*Epoxy, ”five minute”™………………..28 lb
*Cyanoacrylate, ”Slow-Gap”™……….. .30 lb
*Fish glue………………………………..33 lb
*Rabbit skin canvas sizing………………34 lb
*White glue on surfaced wood………… .35 lb
*Commercial liquid hide glue…………. .35 lb
*Sinew glue……………………………….36 lb
*Bone glue, sold as hide glue………….. .36 lb
*Yellow glue …………………………... .38 lb
*Hide glue……………………………….38 lb
*Cyanoacrylate, ”Zap-Gap”™…………..40 lb
*Fish bladder glue……………………….40 lb
*Knox™ gelatin…………………………42 lb
*Epoxy ”Two-Ton”™…………………..44 lb
”Above about 35 lb the maple samples themselves begin to fail. Relative strengths of the strongest glues are therefore less dependable, resulting from interpretation of failure rather than simple measurement”.
Av intresse för de som bygger bågar är följande påstående:
”Earlier in the century spliced billets were commonly joined with casein glue. Few failures were reported, so we can assume a relative breaking strength of about 20 lb (based on the above test) is adequate for handle splices”
Tyvärr står det inte någonstans i texten vilken längd som har varit mellan provet och vågens fästpunkt (dvs. hävarmens längd) men i boken finns en tydlig och klar bild som man bör kunna mäta ifrån och åtminstone få en ganska bra approximation. Tyvärr har jag ingen bra linjal till hands för tillfället.
Ha det...
/Angus