Glue Lines

I use the hide glue from Dick's and mix it 1 glue + 2 water. Heat it till I have difficult to keep finger in the water pan were the glue-pot floats. And I heat the core and horn in my car a sunny day, it's about 40-50 Celsius. I use clamps, many small to apply even pressure over the horn. I make one limb in morning and the next in the evening, haven't more clamps. And have not have any glue line failure yet.
In case a small part is not tight I heat it with heat-gun and clamp it :)
The glue will be soft and sticky and will cool and bond.
Rope gives a better glue-line but can twist the core and need more adjustment.
Ones I left a bow with string on in the car and 10 minutes later it had twist 45 degree but I just turn it straight and it still shoots.

Mike; I would make a sample of scraps first to get the process and timing down. To me the necessary element is getting gelled glue to squeeze out on demand, to fill any empty spaces.

I start with watery glue, about a tablespoon of pearls in a cup or more of water. Imagine the volume of dry glue filling a narrow void between the slats.

Put the glue pan in a double boiler. You are only making bath water. The surfaces are flat ,dry and rough; rough like a rough rasp makes on horn, A metal cutting saw blade used as a scraper diagonally is good. The watery glue goes on with a cheap Chinese caligraphy brush, evened out in the reflection. Lay flat as possible. Now I use a fan to expedite the process pointed at the horn and wood.

The first coat may take half an hour to dry, the next just a little less. When you keep the glue warm water evaporates at a good rate. It is necessary to keep adding small amounts of water but you want the glue to thicken anyway , like cream at the end.

By applying thin glue and drying with the fan the process is speeded up. The Korean in Thomas' tape works in the sun.

After about 15 coats are dry, the wood has turned the color of the glue and drying time is now down to 5 minutes. You have built up a noticeable coat.

Warm the two parts slightly after applying a WATER coat. The water will penetrate to the lowest layer making a viscous mass of the glue.

I always use inner tube strips to assemble. If there is a problem area without squeeze out apply water with the brush to the edge and capillary action will draw the water into the joint. Heat just slightly and the tube strips will squeeze out viscous glue.

Always leave a space on the tube strips to check what is happening. A second layer of strips can be added on top of the first. The bow is shaped and checked for twist etc, maybe applied to a form if things are complex. Let dry several days. Remove bands and dry more.

Before the glue up I assemble dry many times with the tube strips to check everything out. Preparation is everything.

It is no mystery to a woodworker that clamping produces uneven pressure. But I realize that some pretty good bow makers use that technique. -j-

While Jack's post follows the Korean method, there are a few critical steps that are missing.

If your glue gels so fast, you really need to mix in some slow gelling glue to your hide glue. Use bladder glue. The surfaces are not rasped, but scored evenly lengthwise to produce a series of shallow grooves. The strips, sized with the watery glue, are dried on the side, so the excess of glue does not collect in the grooves. The thinner the glue for sizing, the better the strength of the joint, but the number of coats must be enough to make the surfaces glossy (it maybe as many as 20 coats). The strips and core should be well warmed before joining. Use the rope method or clamps to bind - there will be more pressure while the danger of the starvied joint is eliminated anyway with the thick layer of glue already present on the parts.

Good luck.

Adam

You're not on your own, Mike, I found exactly the same with hide glue and this awful summer doesn't help with temperatures hardly reaching 20 celcius.
I am sure you also began to wonder about preparing the sinew and glue and leaving it to gel before gluing to the limbs. The way my hide glue was drying it would be a hard task and I'd imagine combing the sinew and glue would be nigh on impossible.
Adam, mixing isinglass with hide, what sort of ratio would you suggest?

This very interesting topic has been discussed many times in this forum before, but it is still interesting to learn from each other. Very often I get my answers from the search function of this website.

I highly recommend the link from Yokhua how to prepare fish bladder glue (issinglas) http://www.atarn.org/FAQ/fish_bladder_glue.htm and/or the topic "Glue" http://198.170.108.27/phpBB2/viewtopic. ... c&start=15

Personally I put on about 8 - 10 layers of glue onto the core and the horn, beginning with thin issinglas (www.dick.biz, 450142). After 5 layers I start mixing the issinglas with hide glue (www.dick.biz, 450143) ? the glue is now getting slightly thicker. The ratio is about 2:5 (Issinglas:Hideglue). To brush the glue, I am using a glue brush (dick.biz, 706105) and I always let the layers dry thoroughly.

In my home country the weather is sometimes is also cold, rainy and chilly. I developed a personal way/procedure I am very, very happy with and I like to share with others. For the clamping, I prefer the wedging technique http://198.170.108.27/phpBB2/viewtopic. ... sc&start=0


My way:
1) I prepare the materials (wedges, tapes, hammer, string, hot air gun, simmering glue, etc. AND a separate pot with boiling/steaming water)
2) Then I heat/warm up the horn on the belly side with a hot air gun
3) Before burning it, I stop and hold the horn strip over the steaming water to make now the glue glossy and melting (with gloves only)
4) After few minutes, I put on a thick coat of glue over the entire surface of the melting glue and put it aside (e.g. warm place, next to the oven)
5) Now, I take the bow and also hold one limb over the steaming water as well, coat it with thick mixed issinglas and hide glue
6) Both parts are now ready for the wedding
7) I fix the horn with 4 or 5 clamps onto the core, then I replace them with tapes, so the two components cannot slip away anymore
8 Now, I heat up for a very last time the horn with the hot air gun
9) Then I put on the string/rope and use the wedges to bond the components
10) At the very end I am holding the entire limb with the wedges for few minutes over the steaming pot. This helps to keep it warm. Sometimes I even put the bow over the pot and cover it with a towel but before this I lower the temperature by adding some cold water. Now it can stay there up to 30 minutes.


Best regards
Reto

Thank you all for your very informative and useful replies. I'm hugely grateful for all that you've posted. I shall get down to business as soon as I have a nice warm window, and then get back to you all with my next line of questions :D . Perhaps next year I'll even sinew the thing!
I must say though, that even though I've not yet produced a good hide glue glue line, I absolutely love the stuff because you can take the joint apart if it looks bad (luckily without core damage).
I was under the impression that when combing sinew you combed it wet (in water) and then dipped that into warmed glue and then applied. I'm sure that's another kettle of fish though.

Thanks again

There's also the 'ya-ma' - the device shown at image #14 here:
http://www.atarn.org/chinese/making_chi ... ng_bow.htm

You could rig one up easily to help increase the pressure when binding after gluing.

I find the re-heating the clamped parts to be risky. The heat causes the glue to re-liquify between the parts and this may lead to voids. The idea is to keep the joint full of glue until dry.

Adam

Adam; When you say clamps, what type do you mean?

Reheating after assembly when done with innertube strips is not a problem as the slack will be immediately absorbed. The assembly time is increased. -j-

Re-heating after assembly, I mean to w a r m it up again to increase the assembly time to fix the string/rope and finish the job with the wedges resp. wrapping.

Jack you remember, last year on the first evening of the 1st Korean Archery Festival, during the demonstration on the stage, the bowyer did the same with his bow. He wrapped the components half with the jig, stopped warmed up the limb (horn) on the electrical oven and then continued, resp. finished.

The purpose is to extend the time - so far no failures.

Reto

Actually, I've been thinking, testing and proved, that reheating the bounded core (and horn) is quite useful. Yet, I was using hemp ropes and binding tools. For the clamping method, I don't know.
For my binding process the core will be twisted a bit especially the core is thin. The rope acyually works like the combination of clamps and ruber bands together, like many many clamps stay together, yet still got extra tension. After couple hours of binding, I reheat the core and horn by using charcoal in low heat, then gentlely correct the twist, in the mean time some glue will melt again then fill up some gaps or slits, the rope still got extra tension to bound the materials even closer. SO my point of view is reheating is very useful, but only using rope and bound tools. As for the clamping methods, maybe the clamp will loose .. That's my experience..

Yes Reto, if the re-heating is done prior to assembly, it is not only good, but also essential for this operation. Instead of re-heating, if I see that the glue begins to gel before the binding/clamping is finished, I flood the surfaces with hot thinner glue to re-activate the existing (now gelling) coat of glue. But I would not re-heat after the clamping/binding is done, because I want the glue in the joint to stay there and not move. As the gelled glue dries between the parts, the forces of drying tend to close the joint to a degree, in addition to clamping. I also make sure there is a good excess of glue, like a fillet, along the sides of the joint (this in addition to normal squeeze-out) and I add more glue as needed there. The horn-core joinery is too important to risk failure, which manifests itself long after the bow is finished. The bow may look ok during construction, but may still fail after many shots when the horn delaminates. In this respect I do not agree with Yokhua about the re-heating the bound parts and I know there are others who do the re-heating as well.

As to the rope binding vs other methods. If horn strips are flat on the belly side (outside) the rope does not exert any pressure along the centreline of strips. This can be improved somewhat if the strips are straighter than the core (this is due to the Poisson effect the strip is subjected to when bent onto the core, forcing the edges to oppose the pressure of the rope, thus adding more pressure to the centre of strip), or when the horn is round on the outside. Another way is to add padding, such as a piece of thick rope in the Korean method, along the centre of horn strips to be bound together with the strips and the core. This complication led me to use C-clamps over the binding first, and then to abandoning the rope method altogether. I now use only C-clamps every 1 to 1.5 inches along the limbs with good padding.

I also do not believe the innertube is a good way to clamp, since the rubber is too flexible for sufficient pressure, especially when hot during the process of clamping, plus it slows the drying of glue, not to mention the deficiencies similar to the rope method. The wedge method may be good, provided the wedges are placed every 1-1.5in to even-out the pressure in the hot (and therefore softer) horn strip.

I should add, weak pressure during clamping leads to the use of excessive amounts of glue, because more glue provides the this nice, soft/viscous layer to merge the parts. However, the excessive thickness of glue may affect the durability of bow, since the thick glue, as the weaker layer in the bow, "crystallizes" - cracks when the bow is flexed in use after some years.

All this does not mean one can not be successful in making bows whichever method he chooses. It is just the matter of calculating the risk involved.

Adam

Thank you all, I am finding this most interesting. Before I proceed I must point out that my weather is quite different than other's; It was 38 C today with some rain and will be that way for months.

I can imagine that through the centuries, bow making happened in a workshop dedicated for that purpose.

When I described preparation of the surfaces I forgot to ask what type of bow was being built. In actuality, the Korean method requires grooving the horn surface but these are done randomly. That is to say that the grooving tool has no guide and so the grooves are somewhat like fingerprints, grooved but random, not matching to the bamboo core.

I have an old bow made in China which is broken and the surfaces are like I described earlier, with random rasp marks made on the diagonal. There are also some miniscule random lateral scratches on the horn. Please someone convince me that matching grooving has some antiquity in other than Turkish bow making. I do not believe that Huns match grooved horn, never heard it mentioned. There is ONE Egyptian bow drawing but do not know if it is supposition or if the grooves could actually be seen.

How do you prepare your horn and core surfaces? I appreciate everyone's efforts. -j-

I have an old bow made in China which is broken and the surfaces are like I described earlier, with random rasp marks made on the diagonal. There are also some miniscule random lateral scratches on the horn. Please someone convince me that matching grooving has some antiquity in other than Turkish bow making. I do not believe that Huns match grooved horn, never heard it mentioned. There is ONE Egyptian bow drawing but do not know if it is supposition or if the grooves could actually be seen.

Here is a photo of scoring on a Hun bow from around 350AD from Loulan. It is scored; but this core was not accompanied by the horn. The Hun bows I have do have scoring on the horn; but it is not matched. I tend to agree with you that matched scoring was not common.

S

Jack:

There is absolutely no evidence of matched grooving in old bows, Turkish or otherwise. Bows were not made with matching grooves. The grooves were never matched. Even the period toothed scrapers would not allow for such matching. The only matching grooves I saw were on bows by the German maker Mebert.

The grooves were, however, at least in better/stronger bows, well defined and always parallel to the limbs. Diagonal scratching may lead to breakage or delamination.

I think this question came up many times before on this forum.

Adam

ALL of the old medieval hornbow crossbows that I have seen the inside of have matched groves between all the horn strips and between horn and wood, if wood was used.

Adam Karpowicz wrote:

Jack:
The grooves were, however, at least in better/stronger bows, well defined and always parallel to the limbs. Diagonal scratching may lead to breakage or delamination.
Adam

Adam, my observation is different: most of the grooving I see is not parallel to the grain of the wood. On the contrary, there seems to have been some effort to break up the fibers/grain along the gluing surface. While I agree with you that such scording should give rise to breakage, could there have been some trade-off in terms of penetration of the glue?

As I know you're good at maths, if you had, say, 25cm2 and you chose to score it perfectly with grooves of, say 2mm depth in a V, would the total resulting surface area be greater if you scored two sets of grooves on the cross (i.e. little pyramids) or just parallel grooves like furrows ploughed in a field? (Not of course that anyone would do that in practice.)

S

Adam; the scratching that I do is much shallower than you might think. I just use the hacksaw blade in one hand and scratch. Of course my bows are all less than #50 but then Hunnic bows were also made this way and were powerful but longish. So the materials were not so stressed as Turkish bows.

I feel confident of gluing technique. Yokhua, how are you preparing horn and wood surfaces to glue? And others? Jack.

Looking at some of the grooving tools posted, I had my concerns about the 'lining up' situation. If the two surfaces did not line up there would surely be a case of lines of thick glue (voids) and lines of next to none (where the tips touch)
XXXXXXXXXXXXX...a bit like this
Like Jack, the tool I am using is improvised (a cutting blade from a wahl hair clipper)

This is a good point about the crossbow construction. Perhaps the matched grooves in crossbows gave rise to the myth of matching grooves in bows?

Stephen: You are right about the greater surface area with identically spaced diagonal grooves vs parallel. The resulting surface would be a series of raised romboidal pojections. The fibers of horn and wood would be however cut across weakening the materias. It is possible the bows, with wider limbs and with less reflex in the bending section (regardless of the reflex in the grip), which are less stressed, can have diagonal grooving as you say. I used diagonal grooving and not-quite-parallel grooving on some bows with bad results. I also saw a Persian bow where the grooves veered to diagonal in one spot and the bow clearly broke right there. My conclusion is: it is not worth the risk to make any kind of grooving other than parallel. It is just too much work to make a hornbow.

The other issue is the penetration of glue into the surface. The more "roughened" is the surface, the less contact there is between the glue and the material. It is because the glue has limited time to enter all irregularities before it become too thick as it gells. This time is extended in hot climates or in the case of non-gelling glue (depending on the ambient temperature). Any void in the groove or under the "furrow" will expand as the glue dries. The collagen-based glues advantage is their ability to bond to these materials, so contact is essential. If the joint is full of glue, then there is the additional effect of a mechanical bond as in epoxies. In case of epoxies, there is the mechanical bond only, but the wetting, and thus the penetration into the surface is better than the water based glue, so all voids are filled. With such glues the roghened surface is better.

The risk of failure will vary depending on the type of glue, its concentration in water/viscosity, on the gelling time, the ambient temperature and on the type of grooving. I try to minimize all risks as much as I can. In fact, I actually do matching grooves on very stressed bows, even though there is no evidence this method is traditional.

Adam

I do just some scrape with hacksaw blade and in is good enough for 70-80 lb 48" bows.

I've come to a view that for historcal, well-made hornbows, wooden cores are a carvable, moderately water-absorbant medium that allows the additional materials to be assembled by gluing. I have said before that 'good hornbows are made of glue'.

Adam and I have discussed before what role the core plays: it is at the junction between the extension force and the compression force and takes up the shearing force. (Discussed on p. 20 of 'Archery Traditions of Asia', to which Adam made important contributions.) The question in my mind is whether it is the wood (or bamboo) that plays that role best, or instead a highly-penetrative glue of the correct quality. Understanding that issue could lead to a better appreciation of hornbow construction issues.

Grateful for views.

You can make a bow with bad glue :( like epoxy but you can't make a bow with bad core-wood.

Absolutely. Every component in a composite has a role to play. The material propertes are a part of a book I am writing. There will be a detailed discussion of the glue layer with the mechanics involved.

Adam

I know it's not a popular method ,but after cutting my horns into strips ,I soak them for a couple weeks to a month in hide glue that is just thin enough to not gell .Or until they are slimy and flexable . This last time I used milk instead.

I can then bend the horns to flatten or uncurl them with no boiling .Or with just a little added heat ,(like heating hide glue ) I have several minutes of working time to get them clamped or tied in place.

In this picture ,the top horn strip and the second from the bottom strip ,were soaked in milk till pliable . The other two strips were just cut out and sanded flat . In the picture ,I have just applied the first thin coat of glue .

[external image]

Notice that glue on the two soaked horns is even and smooth ,and on the two horns the glue is pooling up and even pulling away from spots leaving dry and glueless areas.

Warmth and the coating with a very thin solution of glue are very important for the glueing- success.

I don?t think that the grooves are to important for the quality of the glue- lines of a hornbow. But I make matched grooves if the bow will be more than 55lbs, and it depends on the bow?s design.
I think adhesive power does a great job, if you don?t make grooves.

If I make grooves I cut the core and the horn a bit thicker. I can?t believe that grooves are not matched, cause if they don?t match, the possibility to end up with voids is great. If the grooves match closely, the surfaces of horn and core are interlocked and assured.

I believe too, that the grooves are done to keep the bow in a straight line, cause a grooved cross- section is more stable.
And the grooves prevent the materials to slip away when you glue them.

(Matched) grooves have important advantages.

Stephen, due to my experience the hornbows done without a core, only made of horn and sinew, like Native American sheephorn- bows, become very hard over the years, a core is somehow preventing it. This type of hornbow is much more dependent on the environmental conditons too.
So a core produces a kind of balance between the sinew- backing and the horn.

Michael

Rwelch wrote: This last time I used milk instead.

Doesn't mean you have to do a lot of work to remove the fat/oil before gluing? Why milk?

I saw an interview on a Discovery Channel show ,(one of their series Digging for the Truth) with the Mongolian bowyer Tumurhuu Batmunkh .In the interview he described using milk in the same manner I had been using hide glue . I have sense bought one of Tumurhuu Batmunkh's bows . I love the bow , he seems to know his stuff , so I gave milk a try . I didn't do anything to try to clean the the horns . I tied them to board to straighten and flatten them a bit . Then after they dried I sanded the inside of them flat.

[external image]

The horns settled to the bottom with the curds and other solids .Maybe it works because milk makes casein glue ?

they were in the milk a month .In that time the milk had completely separated .The horn strips were at the bottom under a couple inches of solids .And the fats and other light material had all floated to the top ..

I scooped the floaties off the top a few times ,because it was growing green stuff. It really did smell pretty bad , not as bad as brain tanning hides ,but close . :lol: :roll:

We never got to an ending on scoring/grooving components for horn bows.

Adam, can we assume that you are using some kind of guide to make the groovings "even" ? Do you also groove the wood? If these do not drop down into eachother then there must be a flat area between the grooves left? Jack

they were in the milk a month .In that time the milk had completely separated .The horn strips were at the bottom under a couple inches of solids .And the fats and other light material had all floated to the top ..

This is getting very interesting. In Mongolia, there is more chance that they were using mares' or sheep's milk that cow's milk. If it's mares milk, and the low humidiy/temperature, they would probably end up with the horn in a very acid whey and the curds floating. The whey would be strongly acidic with a good deal of bacterial matter. I would be intersted if someone could give a view on what the glop that the horn ends up lying in would be composed of and what its properties would be.

Another point is that Mongolian hows have horn from the sheep family rather than the ox famile. I don't know if that makes a difference. Sheep horn is relatively brittle, and the acid/bacterial treatment from the whey could reduce calcium levels while not affecting keratin.

Any ideas, everyone?

S

Steven , the horns I used this time are gemsbok .You may be on the right track ,because they do feel more like buffalo horn now .Smoother and less brittle . This was my first time trying milk ,and yes it was cow milk ..Maybe I should try goat milk ?

I have used this method with hide glue instead on gemsbok ,and domestic goat and sheep horns ,with the the same effects.

Here is the bow the horns are on , if you want to see it.

http://paleoplanet69529.yuku.com/topic/17846

I didn't post it here yet ,because the level of skill here intimidates me a bit.

In the last two days, I have finally achieved what I deem a reasonable job, although if it delaminates I won't be all that surprised. The glue line is consistent and in most places less than 1 mm (if at all) and in some unfortunate areas (though not on the bending limb) less than 2mm. Where there are little gaps I shall fill with extra glue if necessary, none of the gaps propagate for more than 0.5mm.

This time I:
Heated thick and thin glues in water bath,
painted both horn and wood with thin glues till I ran out of the stuff,
then painted on one layer of thick glue on each,
Evened out the surface of the glue by using water and a heat gun, it really works like a charm. The fact I could de-gel the glue gave me as much time as I liked,
Wrapped with inner tubes as Jack suggested (although next time I will use ropes and clamps, I think it may be tighter).,
Left for 24hrs:

I must also add that it was between 30-40 degrees in the sun when I glued. This is probably the critical point.

Below are my results. A big thankyou to everyone who has contributed to this thread and any other in which I've asked for help, I'd never have gotten this far without you. Next stage, sinewing!

Also, an unrelated question, could anyone comment on the size of my ears? Should I leave them as they are for safety, or thin them down for speed?

Mike; That is a very good start, conservative bend for a starter. Am glad to see the glue squeezed out.

Tube strips for gluing horn should be 3/4 inch which will stretch out to 1/2 inch wide. I stretch them almost to the stopping point. Another advantage of using tube strips is that the horn can be drawn together tightly in the middle. Never mind that. Just neatly cut and glue a horn or bone block in center.

A well known adage of woodworkers is that the clamping pressure does not need to to be so great if the fit is close.

What kind of surfacing did you do on the glued faces? Jack

and yes it was cow milk ..Maybe I should try goat milk.

No, that's going to the higher-fat-content end of the spectrum. You need a thin milk. I would actually go for the lowest fat cow's milk you can find. I suspect hat it's only the whey that we're interested in. Mongolians will be using milk from mares or sheep, and it will be unpasteurized.

S

You can always remove wood from the ears later so let them be till you shot.
Handle looks fat and short fades. Take down the handle before sinew, sinew will add thickness.

Hello Hardman,

Nice work at first.

Did you glue the horn to wood without groovings ?

I canot see groovings in the Picture "horn gap".

I left the gap on the basis that when the sinew is applied, a gap is made regardless, and my horns were a wee bit too short. I'm definitely buying overlong horns next time.

Surfacing-wise, I only grooved lightly with an old saw blade. You can't see any in the gap for two reasons, the grooves (scratches might be more appropriate) are very thin and there are two layers of glue over them.

Redhorse, I was thinking that about the handle as well. I'll not be able to get my fingers round it if I left it as it is! Thanks for the point on the ears.

Forgive me if I do not reply to any more comments, I'm losing internet access for a while.

Mike, it's great to see you had a decent day to carry out the job. The bow is looking good, congratulations.

The limb horns don't need to be all the way. If they are under the handle fade it's enough. You can put a piece from the horn sides in between to fill the gap. Same at the kassan, if horn goes under the point of spice it will hold.
But of course, longer horn is to prefer.
On next bow I will have thicker horn under handle so I can make the belly side of handle more narrow and round. Flat handle is not good.

Hello everybody,

Which glue is best for Wood to Horn ?
Which glue is best for Sinew backing ?

Is it Hide Glue or Fish Bladder from Sturgeon ?

Is there a visible difference between this 2 Types of glue ?
Or is one more flexible and one more stronger ?
And which one is better for humidity after years for the bow ?