Both the Shulchan Aruch Harav and the Mishnah Brurah use similar terminology when describing the importance of the shin being "pointy" on the bottom and all three branches of the letter shin meeting at a point or "chad" at the bottom of the letter. There is a strong foundation in Halacha for this and for the bottom of the shin to be flat like a moshav (base) is considered questionable (Pri Megadim) and definitely not Kosher Lechatchillah. It is worse if the moshav is very wide, but it is still questionable if it is lechatchillah if there is a thick noticeable base rather than a chad.
Even for Sephardim, who lechatchillah make an angular base, it is still important that the base is indeed on a (significant) angle. If the base is flat, even if all three branches of the shin come out of the base connected , as in the top picture, it is problematic. It is worse in the bottom picture below where the right head/ branch comes out of the right part of the base and the mi…
PVC is not known as being a strong glue. I don't know its kosher status.
ReplyDeleteSuper glue is a brittle glue. When gluing flexible things, like klaf, it can crack over time. I don't know for a fact its kosher status, but, from what I know about the chemistry of how it is made, I don't see a problem. This is true only for the professional glues, professionally known as cyanoacrylate.
see http://en.wikipedia.org/wiki/Cyanoacrylate
I don't know what other additives may be added to the home-grade glues.
The best adhesive for stam is the yellow wood glue made by Elmer's for carpenters. It is strong and somewhat flexible. Best for gluing klaf to klaf. I checked with a chemist at the company and he assured me that all their glues are synthetic, no animal ingredients.
If you want "Elmer's wood glue" to be more flexible, for whatever reason, you can mix it with a little white "Elmer's glue all". It will make the mix more flexible and LESS strong.
ReplyDeleteNever use school-glue. It has no strength.
A word of warning -
ReplyDeleteLast time I checked my Tfillin, the sofer told me to melt a black crayon to fill in the cracks between the top and bottom parts of the Batim. It sounded suspicious to me, so I called Crayola company that makes these crayons. They said that they use stearic acid in the crayon. About half of the stearic acid they buy is vegetarian, and half is from animal fat, which could also include pig fat. Then, they mix it all together.
Beware.
Perhaps a more kosher method would be to mix lampblack with melted beeswax instead of crayola.
DeleteI would recommend using parchment/hide glue. It's a protein based glue produced by boiling small snippets and scraps of klaf, or cow rawhide. Parchment size is very good for gluing anything on klaf where a lighter glue is required, while hide glue is much stronger and could be used where more strength is required. To make either simply simmer a handful or two of parchment clippings over a low flame for several hours. Allow the liquid to cool, as it does it will solidify into a firm jelly. Cut this up into small pieces and allow it to dry. When you need glue mix one part dried glue with one part water and allow to melt in a double boiler. Under no circumstances allow it to boil. The reconstituted glue should have the consistency of honey and be light in color.
ReplyDeleteCow rawhide can be had from many craft supply stores, and also from most any grocery store where it is sold as a pet chew for very little.
If you need a glue with even stronger binding properties, follow the above procedure but use fish bones and cartilage instead. Fish glue is the strongest of the natural glues and is very good on wood, such as broken atzei chaim and anywhere else where an extremely stong bond is desired. I'm told it's even stronger than epoxy.
If you don't care to make your own, very good glue can be had from kremer pigments. They state plainly that their hide glue is made from cow hide.