Pinning hopes on bullfrogs

Tanning bullfrog skins could prove to be an alternative source of raw materials for making leathergoods and footwear products in the Phillipines. Leather experts in the country have succeeded in enhancing technology which they intend sharing with those interested in making it a business. A source of meat for some people, the bullfrog or the giant South American toad (Bufo marinus) is becoming a byword in the local leather sector after a successful study on the efficient processing of its skin. It is now considered as a substitute for hides and skins in the local markets. Government researchers ventured into the experiment after they had noticed that bullfrogs were abundant everywhere in the country, and they decided that its development could contribute in enhancing the supply of quality leather in the country. Local business has been heavily dependent on imported leather as primary components for the production of various leather crafts, but now the Bureau of Animal Industry's Animal Products Development Centre (APDC) in Valenzuela City has proved that frog skin can be used for making leathergoods such as bags, shoes, bracelets, watch straps, sun visors and fashion accessories. Dr Corazon Maza, newly installed chief of the APDC, has co-authored a study that shows how tanned frog skin could create a name for the Philippines as an exclusive supplier of small skin leathers in the world markets. 'The only problem is that some exporters of leathergoods made from frog skins do not want to share their trade and technology secrets', says Maza. 'That's why we have experimented on our own ways of processing the frog skin that could be used for commercial purposes. We do this by holding training seminars at the centre', she said. One constraint that could damage the hopes of entrepreneurs is the Republic Act 9147, otherwise known as the Wildlife Resources Conservation and Protection Act, now being implemented by the Protected Areas and Wildlife Bureau (PAWB) of the Department of Environment and Natural Resources. The PAWB is tasked with regulating the collection and trade of wildlife, which includes frogs and toads. 'The cultivating and propagation of frogs under controlled condition would be a legitimate way for any commercial use of the frogs', says APDC tannery chief Faustina P Odiña, another co-author who, along with Hernando Diaz, wrote the study entitled 'Development of Tanning Techniques for the Efficient Utilisation of Frog Skins.' Economic analysis Leather manufacturers heavily rely on costly imported raw materials for the production of leathergoods and footwear products. Government data showed that over the years, the sale of locally-made leather crafts have performed well on the open market and has earned substantial income for the domestic economy. The National Economic and Development Authority noted that the Philippines earned an average of US$62.3 million between 1982 and 1984 from its exports of leathergoods and footwear products. Major markets are the US, UK and Australia. The study also noted that the Philippines' share was only 1% of US leather imports in the 1980s. However, this is equivalent to about 80% of the Phillipines' total leather footwear exports. In the UK, the country's share is less than 1%, while Australia absorbed less than 4% of local exports of leather footwear products. The Bureau of Export Trade Promotion said that in 2001-2002, exports of leathergoods declined considerably. Local manufacturers admitted that the trend was due to a big increase in domestic sales, which meant that local demand for domestic goods increased leaving them with no option but to concentrate on supplying the local market. Despite this positive development, the industry was constrained by the high cost of imported chemicals, thus affecting its profitability. 'Another reason is the lifting of the export ban on raw hides, thereby resulting in low production rates. The third reason is the closure of some tanneries due to their non-compliance with the government's environmental regulations', the study said. The United States is still the leading export market for Philippine leather crafts. This is followed by Japan and the UK. From the total volume of leather products exported to these markets, less than 1% is currently made from frog skins. 'With the introduction of the exotic frog skin leather in the footwear and leathergoods industry, the Philippines is now aiming to widen its horizon in the world market', they believe. For a start, enterprising people are encouraged to start their own backyard tanning business with a minimum capital of about $400. In fact, the cost of production per 50 pieces of frog skins is more or less $7. Frog skins are not so expensive compared with other larger skins, for instance, a wet-salted frog skin costs about 10 cents. But for commercial purposes, propagation and culturing of the frogs will promote a steady and cheap supply of the frog skins without disrupting the ecological balance. The study has clarified that with the right combination of tannages, leather from frog skins can be an income earner for the backyard tanner and small entrepreneurs. This is because its processing does not require expensive tanning machineries as it can be done in the backyard or in the garage. 'Unlike the heavier hides and skins of cattle and carabao and the ruminants, frog skins are very light and smaller in area by comparison. Since frogs reproduce at a very fast rate, especially during the rainy season, the supply of frog skins should not be a big problem', they added. Leather experts have suggested that those who would like to engage in large-scale business can opt to farm bullfrogs in line with the government's environmental protection regulations. Treatment procedures Based on the study, six efficient procedures to process frog skins have been suggested (Table 1). The study suggested that the beamhouse operations should be used for all treatments. In their experiments, they used 300 pieces of wet salted frog skins (50 pieces per-treatment), which underwent the same beamhouse operations, from soaking to pickling. In the process, the skins are soaked, usually overnight, in a bucket containing 400% water and 0.2% bactericide based on the weight of the frog skins. The following day, the skins are piled to remove excess water and then weighted. The soaked weight is recorded, and this is taken as the weight basis for liming and reliming. For liming, the skins are placed in a pail containing 400% water, 5% lime and 3% sodium sulfide. It is left in the solution overnight with occasional mixing. For reliming, the skins are then placed in a bucket containing 400% water and 5% lime and mixed occasionally. Descaling and fleshing are done the following day. The fleshed weight is then measured for subsequent processing. For deliming and bating, the pelts are place in a bucket containing 150% water and 3% ammonium sulfate. After 45 minutes of mixing, 1% bating agent is added in the same solution. It is mixed for another 45 minutes, and then washed with water to stop the action of the bate. A bleaching process is carried out to remove the natural colouring of the frog skin and to avoid masking the colour of other dyestuffs that will be introduced into the leather later. The pelts are placed in a pail with 800% water and 30% salt. Then 4% formic acid (diluted x10 with water) is added gradually. It is mixed for 15 minutes after the last addition of acid. Then 30% hydrogen peroxide is added to the pelts, and mixed for 10 minutes, followed by 2% formaldehyde. The pelts remain in the solution for 24 hours. The bucket is covered to prevent fumes from escaping. Next day, 15% of sodium bisulfite is added to the solution and mixed for an hour. In the pickling process, the pelts are place in a bucket containing 400% water and 12% salt and mixed for 10 minutes. A mixture of 0.5% sulfuric acid and 0.5% formic acid diluted with water and added in two portions and mixed for four hours. After pickling, the skins, including the float, are equally divided into six portions to proceed to the specific treatments. For the full chrome treatment, tanning is done by putting 6% chrome powder into the pickle liquor in two portions at an interval of 15 minutes. The skins are mixed for an hour or until complete tannage is achieved. Complete tannage is checked by cutting a small portion from the thickest part of the skin and noting if the cross-section is uniformly bluish green in colour. Once the preparation of chrome is complete, sodium bicarbonate is added to elevate the pH and mixed for 45 minutes. The bucket is drained and the skins piled for a day to fix the tannin. To neutralise the leather, it is placed in a pail with 400% water and 1% sodium bicarbonate and mixed for 45 minutes. For dyeing and fatliquoring, the leather is placed in a pail with 400% water at 50ºC and 1% acid dyestuff and is mixed for 45 minutes. The fatliquoring agent, 4% Lipoderm Liquor IC, diluted five times, was added gradually into the dye solution then mixed for 45 minutes. Then 1% formic acid (diluted 10 times with water) is added in two portions at 15 minutes interval. And this process takes about 45 minutes to finish. The leather is piled to remove excess water. Then it is placed on wooden frame, grain side up and nailed at the sides. Drying usually takes one day. When fully dried, the flesh side of the leather is buffed with sandpaper to obtain a smooth surface. Finishing is achieved with a glazeable binder and a fixation coat. In the absence of a commercial binder such as Luron Top which is not always available, a combination of egg white, evaporated milk and water is used. The proportion is two egg whites, one part milk and two parts water. For two egg whites, use 50ml milk mixture. The glazeable binder is applied on grain of the leather, and dried for 10 minutes. This process is repeated only once. To produce gloss, the leather is passed under a glazing machine or, in the absence of the machine, rubbing briskly with a bottle can achieve the same sheen.