Madura? dagger

[JamesKelly]

I'm new to this, have picked up a few points about flint & percussion American arms over the last three-score years, but am learning of my abysmal ignorance regarding knives. Well, perhaps the learning process will help stave off dementia just a little longer.

Was told by a helpful forum moderator that this was a spear, tombak, made into a dagger. Do similar daggers show up now & again out of Indonesia?

Whatever it is I like the bone carving & horn trim. Don't intend to inquire too deeply about whose bone was used to make it. Photo doesn't show the light and dark areas on the blade well, but it is a layer forged blade.

Is there perhaps a professional chemist on this site who could explain exactly how arsenic trioxide & lemon juice makes that crusty black color on a keris, or this spear/dagger, blade? I am a metallurgist with some knowledge of corrosion, steel and nickel alloys but know nothing about arsenic/AsO3 & how it might react.

I have the uneasy feeling that maybe I shouldn't handle that black stuff too much? Aside from harming the blade finish?

[kronckew]

lots of posts in the keris forum. a search on 'arsenic' or it's indonesian name 'warangan' would be informative. the chemical treatment is followed by a wash in warm soapy water, so the risk of picking up any arsenic is minimal. best not to lick the blade tho.

the daggers made from spearpoints are fairly common.

mine is not quite as decorative as yours.


see also: lading terus at http://old.blades.free.fr/

[A. G. Maisey]

James, here is an extract from the draft of an unpublished thesis. I tried to get the person who wrote it to publish it, but my urging did no good. Because of this I feel it is not correct to name the author. This is probably not exactly what you're looking for, but it might point you in the right direction.

EXTRACT:-

Some possible chemical reactions between iron and arsenic solution

Theoretically, there are numerous chemical reactions which could take place between the iron and the arsenic solution, with the formation of several compounds in the patination layer. In reality these reactions would be complex and their identification falls outside the scope of this paper, however some simple propositions are made.

Arsenic trioxide (As2O3) has low solubility in water, only up to 3.7g/L (Source). However, in strong acids it dissolves to form arsenic acid (H3AsO4): in industry arsenic acid is prepared by reacting As2O3 with dilute HCl (Merck Index date: 136). Although citric acid is weaker it is possible that some arsenic trioxide dissolves in citric acid to form arsenic acid. Parallels may then be found between an iron/arsenic acid reaction and processes involving phosphoric acid, known as phosphating, used for example to ‘blue’ and ‘brown’ steel. Phosphorous is found in the same group as arsenic on the Periodic Table (Group 15), and the two elements and their compounds therefore share many chemical characteristics (Source).

The phosphating process

In the phosphating process, a range of phosphates of varying solubility are formed, from fully soluble primary phosphates to fully insoluble tertiary phosphates. As the metal corrodes in the presence of phosphoric acid, the pH of the solution near the surface slightly increases. This allows the insoluble tertiary phosphates to precipitate on the surface, forming a stable patination layer (Gabe 1972: 130; Selwyn 2004: 105). Gabe (1972: 130-131) provides the following reactions (where M is the metal):

For heavy phosphating with iron, manganese and zinc, phosphates solutions at pH 2-4 are used and reaction commences with metal dissolution:

M + 2H3PO4  M(H2PO4)2 + H2

The oxidising accelerators depolarize this reaction (H2  H2O) and the formation of soluble primary phosphate may be regarded as partially rate-controlling. At this stage the pH rises due to the loss of H+ ions and the secondary phosphate begins to precipitate:

M(H2PO4)2  MHPO4 + H3PO4

If the rise in pH is sufficient tertiary phosphate is formed rapidly by hydrolysis:

3M(H2PO4)2  M3(PO4)2 + 4H3PO4
or:
3MHPO4  M3(PO4)2 + H3PO4

If phosphoric acid was substituted with arsenic acid, a similar process might theoretically occur. Instead of iron phosphates depositing on the surface of the metal, iron arsenates (eg Fe3(AsO4)2, ferric arsenate) may form. Arsenates and phosphates are often isomorphous (Cotton & Wilkinson 1988: 430) so the physical characteristics of phosphated and arsenated layers could be expected to be similar.

‘Blueing’ and ‘browning’ treatments have historically been used to reduce reflectivity on firearms (Pearlstein 1978: 22; Angier 1936: 2). The recipes for these and similar conversion coating techniques are abundant, as evidenced by the literature (Angier 1936; Untracht 1969: 418-419; Gabe 1972; Pearlstein 1978; Matero 1994: 204-208; Gilroy & Godfrey 1998: 123), however most consist of a combination of acids and salts. Angier includes the following for ‘Arsenic grey-black’, using ferrous sulphate or ferric chloride, arsenic trioxide and crude concentrated hydrochloric acid: “Let the mixture stand for a few days until it is all dissolved, keeping in a stoppered bottle and as cool as possible. The degreased parts when dipped or painted with the solution become covered after about ½ minute with a uniform, delicate dove-grey coating; rinse thoroughly and repeat until the desired shade is obtained. Wash in hot soda solution to destroy all traces of acid then with plain water. The surfaces are but slightly pickled: on matted pieces the coating is velvety smooth, on polished ones a brilliant deep black” (1936: 115). More common, however, are recipes stipulating the use of phosphorous-based compounds.

Other considerations and suggested analytical pathway

Another possible reaction may be between arsenic, sulphur and iron, in the instance of warangan (As4S4) being used. A compound containing these elements is arsenopyrite (FeAsS). The formation of black iron oxides such as wüstite (FeO) and magnetite (Fe3O4) is less likely as a strong alkaline is usually required (Pearlstein 1978: 22). A process known as Bower-Barffing produces black iron oxides on the surface of iron using heat and steam, but a reducing atmosphere (eg hydrogen or CO2 rich) is required to convert red oxides to magnetite and wüstite (Matero 1994: 205; Selwyn 2004: 102). Another process where magnetite forms is through anaerobic oxidation of zerovalent iron (Furukawa et al 2002: 5469). The conditions required for either of these processes are absent when keris are patinated. A further possibility is the formation of iron citrate complexes between the metal and citric acid (for example, using the reaction between iron and tannic acid as a guide, see Selwyn 2004: 103-104). Depending on the homogeneity of the solution (for example, if the warangan, which may include numerous impurities, is not ground to a uniformly small particle size); the temperature at which the treatment is performed; and the strength of acid used, it could be expected that many of the above compounds are produced at various sites on the surface.

Two analyses were proposed to obtain a clearer understanding of the types of reaction occurring and the compounds which are formed, however due to insufficient funding and OHS concerns, these were unable to be conducted. The first suggestion was to recreate the patination layer on pieces of iron using arsenic trioxide in lime juice; the conversion layer could then be scraped off and prepared for powder diffraction analysis. The alternative proposal was to directly test the surface of a blade using CSIRO’s micro-XRD facility. As this technique is non-destructive and no sampling is required, a keris which had already been stained in the past could be tested. The CSIRO also has access to a comprehensive spectral database, so identification of the various crystalline compounds detected on the surface would be relatively simple. It is hoped that analysis of this type might be undertaken in the future to provide a better understanding of the chemical processes involved in this traditional technique.

Protective capacities of the conversion layer

Chemical conversion layers are generally thin – characteristically less than 3µm, although some phosphate layers may be 50 µm deep (Pearlstein 1978: 22; Gabe 1972: 129; Selwyn 2004: 105) – and do not afford a great deal of protection against corrosion (Angier 1936: 24). In damp, aerobic conditions the layer is too porous to prevent the iron from corroding, and the film can be vulnerable to chloride and sulphide attack (Angier 1936: 24; Gabe 1972: 130). While some conversion layers do have good wear resistance (Gabe 1972: 130) the fact that keris are traditionally re-stained every year suggests the thin patina is susceptible to wear. Two keris blades in the Leonhard Adam Collection at the University of Melbourne which were examined microscopically displayed signs of wear and corrosion. ‘Proud’ surfaces were silver-grey in colour while the more recessed surfaces remained black, and corrosion products appeared equally in the blackened regions as in the unpatinated zones (Figures x-x). The limited ability of this process to provide lasting protection of the metal surface suggests its purpose is primarily ritualistic and aesthetic, and is connected to the spiritual status of the pamor. Owners of keris appear to accept the inevitable loss of the blade’s surface over years of annual siraman in exchange for a spiritually ‘well-fed’ object.

[JamesKelly]

I am impressed, to understate, at the detail of your reply. Know a little about phosphatizing. Now I shall dig into it in some detail, to help follow this dissertation on "arsenic-izing".

One of these weeks I hope to visit my former employer & of course help them out with some things whilst conning the lab guys into applying their X-ray fluoroscope to a few goodies of mine. Including the crusty black areas on a keris I just got, looking for arsenic just for fun. Hope they don't get too worried if they find As. As has been suggested, I will not lick the blade. If I should find anything, useful or not, I'll post it here.

This site fascinates me with the depth of knowledge you gentlemen display.