CONTENT
1.0 Mersawa Species (preservation and Drying)
2.0 Preservation of Rubberwood
3.0 Pulai Species (Preservation and Drying)
1.0 MERSAWA SPECIES (Preservation and Drying)
The Scientific Name for the Mersawa is Anisoptera spp. From Dipterocarpacaeae family. In , Peninsular Malaysia, Indonesia and Papua New Guinea also known as Mersawa. Mersawa also known in many names such as Phdiek in Combodia, Mai Bak in Loas, Pengiran in Malaysia Island, Kaunghmu in Myanmar, Palosapis in Philippines, Krabak and Pik in Thailand and Ven-ven in Vietnam. Normally, this type of wood have 60 to 150 cm of diameter and the color of wood is orange-yellow.
Mersawa has moderate durability that has to treat with preservative because of the sapwood that not durable to against wood degrading agents. This type of timber is difficult to treat with preservative because this timber is poorly or not permeable timber. It is very susceptible to fungal attacks and termites is difficult to attacks this timber. When we want to treat this type of timber, we need appropriate preservative treatment to treat this timber because the appropriate preservative can against dry wood borer attacks.
Drying rate for Anisoptera spp. must be in slow rate to avoid the wood from damage such as checking, collapse, distortion and so on. Distortion maybe happen when process of drying occurred. The checking of wood also maybe happens to the timber when drying. Normally, when the green wood is use for drying, the air humidity must be higher but the temperature is not to higher. So, when the moisture content is low, the temperature must be is higher and the air humidity must be low from temperature.
For Anisoptera spp. that has the thickness less than 38mm, normally use the drying schedule as below :
MC (%) | Temperature (˚C) | Air Humdity (%) | |
Dry-bulb | wet-bulb | ||
Green | 50 | 47 | 84 |
40 | 50 | 45 | 75 |
30 | 55 | 47 | 67 |
20 | 70 | 55 | 47 |
15 | 75 | 58 | 44 |
For the thickness from 38mm to 75mm, the air relative humidity must be increased by 5% for each increases and for the thickness of timber over 75mm, the relative humidity also should be increase about 10%. For drying process, cares are needed to avoid pocket moisture.
2.0 PRESERVATION OF RUBBERWOOD
The scientific name for Rubberwood is Hevea brasiliensis from Euphorbiaceae family. Other names for Rubberwood is Kayu Getah and Para Rubber. Rubberwood also known as Kausuu in Combodia, Kayu karet and Pokok Getah Para in Indonesia, Jaang in Loas, Kyetpaung in Myanmar, Katoh and Yang Phara in Thailand and Coa Su in Vietnam.
The sapwood of Rubberwood is almost like heartwood which is pale cream in color and mostly with a pink tinge. Rubberwood is classified as Light Hardwood with density of 560 to 640 kg/m3. Rubberwood also classified as non-durable wood because it is very easy to attack by fungi and insects.
Rubberwood is very easy to treat with preservative. Treatment for rubberwood normally takes place when the log is delivered. For this species, the treatment must be done quickly about two or three days after felling. When the process is doing on dry season, the treatment process must be done less than 60 hours but when the process is doing on rainy season, the process must be complete faster than dry season.
The log is given a prophylactic treatment to against wood borer. The normal prophylactic treatment involves of dipping the logs into a tanks containing a preservative solution. Dip-treated and sprayed boards but moulds and other types of fungi still can grow especially during rainy days. So, preservative-treated Rubberwood helps strengthen the wood’s resistance to biodegradations.
The current processing industry in Asia, normally use three types of preservative. That is pentachlorophenol (PCP) compounds, copper-chrome arsenate (CCA) and boric acid solution. The preservative that always used to treated rubberwood is boric acid solution. PCP and CCA are insecticides, while boron compounds are fungicide solution.
3.0 PULAI (Preservation and Drying)
The scientific name of Pulai is Alstonia spp. from Apocynaceae family. Vernecular names for Pulai in Sarawak is called mergalang and Pelai. In Sabah, Pulai is called sayongan. There is many species of Pulai such as A. angustifolia, A. angustiloba, A. macrophylla, A. pneumatophora, A. scholaris and A. spatulata. Also known as Milky pine and white cheesewood in Australia, Popel khe in combodia, Mbulei in Fiji, Chatian and Shaitan wood in India, Kayu susu, pulai, pulai hitam and Rita in Indonesia, Mai Tin Pet in Loas, Lettok, Sega and Shaitan in Myanmar, Chatian in Pakistan, Kajoe soesoeh in Papua New uinea, Batino, Cayacayao, Dita and Silhigan in Philipines, Kra thungfa hai, Sattaban, Teen thian, Thia, Thungfa and Tin Pet in Thailand and Mo cua in Vietnam.
This species is classified as Light hardwood species with a density of 210-500kg/m3. Pulai species is classified as not durable species after the graveyard test for untreated specimens. The timber is known as the presence of latex traces which is normally found at cluster. This species are susceptible to fungal and borer attacks.
Pulai is one of the timbers that easy to treat with preservatives. The drying process is divided into two, which is air drying and kiln drying. For air drying, there is some damage at the timber such as cupping, bowing, twisting, and end-checking. But the damage is very minimal and this is always happen when doing air drying. The timber is always attack by powder-post beetle and fungi. For the timber that has 13mm thick, about one and half month is needed to dry the timber while the timber that has 38mm thick, takes two and half months to dry.
For the kiln-drying, schedule J is recommended. The stain, mould and insects attack still attack the timber while the timber dried fast. Normally, when the thickness of timber is 25mm, it takes 5 days to kiln-dry to reduce the moisture content up to 50% to 10%.
Kiln Schedule J
Moisture Content (%) | Temperature (Dry Bulb) | Temperature (Wet Bulb) | Relative Humidity (%) (approx.) | |||
° F | ° C | ° F | ° C | |||
Green | 135 | 57.0 | 123 | 50.5 | 70 | |
50 | 135 | 57.0 | 119 | 48.0 | 60 | |
40 | 140 | 60.0 | 118 | 47.5 | 50 | |
30 | 150 | 65.5 | 121 | 49.0 | 40 | |
20 | 170 | 76.5 | 127 | 53.0 | 30 | |
